[Bug]: Special character in ical url produce error when adding a new subscription

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

When I add a new subscription in the calendar app I get the following error. The ical url is from my university. The problem is that one of my professors has a "ë" in his name which creates the problem. Also google calendar has a problem with this and just displays a "�" instead, which is fine for me everything is better than an error.

I have tested using the linuxserver.io docker image. I tried the mariadb docker container from linuxserver.io and I tried the offical postgresql docker container. Both do not work and generate the same error.
I also tried sqlite which does work.
Always tested on a clean install.

Steps to reproduce

1. Open the calendar app.
2. Add a new subscription to a ical url. In the description of at least one appointment is a "é".
3. The error appears.

Expected behavior

Like google display a "�" or something similar instead of giving an error.

Installation method

Community Docker image

Nextcloud Server version

27

Operating system

Debian/Ubuntu

PHP engine version

None

Web server

None

Database engine version

Other

Is this bug present after an update or on a fresh install?

Fresh Nextcloud Server install

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

root@f51a07aee6c7:/# occ config:list system
{
    "system": {
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "localhost:450"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "27.0.0.8",
        "overwrite.cli.url": "https:\/\/localhost:450",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true
    }
}

List of activated Apps

root@f51a07aee6c7:/# occ app:list
Enabled:
  - activity: 2.19.0
  - calendar: 4.4.4
  - circles: 27.0.0
  - cloud_federation_api: 1.10.0
  - comments: 1.17.0
  - contactsinteraction: 1.8.0
  - dashboard: 7.7.0
  - dav: 1.27.0
  - federatedfilesharing: 1.17.0
  - federation: 1.17.0
  - files: 1.22.0
  - files_pdfviewer: 2.8.0
  - files_rightclick: 1.6.0
  - files_sharing: 1.19.0
  - files_trashbin: 1.17.0
  - files_versions: 1.20.0
  - firstrunwizard: 2.16.0
  - logreader: 2.12.0
  - lookup_server_connector: 1.15.0
  - nextcloud_announcements: 1.16.0
  - notifications: 2.15.0
  - oauth2: 1.15.0
  - password_policy: 1.17.0
  - photos: 2.3.0
  - privacy: 1.11.0
  - provisioning_api: 1.17.0
  - recommendations: 1.6.0
  - related_resources: 1.2.0
  - serverinfo: 1.17.0
  - settings: 1.9.0
  - sharebymail: 1.17.0
  - support: 1.10.0
  - survey_client: 1.15.0
  - systemtags: 1.17.0
  - text: 3.8.0
  - theming: 2.2.0
  - twofactor_backupcodes: 1.16.0
  - updatenotification: 1.17.0
  - user_status: 1.7.0
  - viewer: 2.1.0
  - weather_status: 1.7.0
  - workflowengine: 2.9.0
Disabled:
  - admin_audit: 1.17.0
  - bruteforcesettings: 2.7.0
  - encryption: 2.15.0
  - files_external: 1.19.0
  - suspicious_login: 5.0.0
  - twofactor_totp: 9.0.0
  - user_ldap: 1.17.0

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

[webdav] Error: OC\DB\Exceptions\DbalException: An exception occurred while executing a query: SQLSTATE[22007]: Invalid datetime format: 1366 Incorrect string value: '\xEBl Kee...' for column `nextcloud`.`oc_calendarobjects_props`.`value` at row 1 at <<closure>>

 0. /app/www/public/lib/private/DB/QueryBuilder/QueryBuilder.php line 328
    OC\DB\Exceptions\DbalException::wrap()
 1. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 2974
    OC\DB\QueryBuilder\QueryBuilder->executeStatement()
 2. /app/www/public/lib/public/AppFramework/Db/TTransactional.php line 63
    OCA\DAV\CalDAV\CalDavBackend->OCA\DAV\CalDAV\{closure}("*** sensitive parameters replaced ***")
 3. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 2932
    OCA\DAV\CalDAV\CalDavBackend->atomic()
 4. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 1268
    OCA\DAV\CalDAV\CalDavBackend->updateProperties("*** sensitive parameters replaced ***")
 5. /app/www/public/lib/public/AppFramework/Db/TTransactional.php line 63
    OCA\DAV\CalDAV\CalDavBackend->OCA\DAV\CalDAV\{closure}("*** sensitive parameters replaced ***")
 6. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 1217
    OCA\DAV\CalDAV\CalDavBackend->atomic()
 7. /config/www/nextcloud/apps/dav/lib/CalDAV/WebcalCaching/RefreshWebcalService.php line 129
    OCA\DAV\CalDAV\CalDavBackend->createCalendarObject("*** sensitive parameters replaced ***")
 8. /config/www/nextcloud/apps/dav/lib/Listener/SubscriptionListener.php line 61
    OCA\DAV\CalDAV\WebcalCaching\RefreshWebcalService->refreshSubscription()
 9. /app/www/public/lib/private/EventDispatcher/ServiceEventListener.php line 86
    OCA\DAV\Listener\SubscriptionListener->handle()
10. /app/www/public/3rdparty/symfony/event-dispatcher/EventDispatcher.php line 251
    OC\EventDispatcher\ServiceEventListener->__invoke()
11. /app/www/public/3rdparty/symfony/event-dispatcher/EventDispatcher.php line 73
    Symfony\Component\EventDispatcher\EventDispatcher->callListeners()
12. /app/www/public/lib/private/EventDispatcher/EventDispatcher.php line 87
    Symfony\Component\EventDispatcher\EventDispatcher->dispatch()
13. /app/www/public/lib/private/EventDispatcher/EventDispatcher.php line 99
    OC\EventDispatcher\EventDispatcher->dispatch()
14. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 2479
    OC\EventDispatcher\EventDispatcher->dispatchTyped()
15. /app/www/public/3rdparty/sabre/dav/lib/CalDAV/CalendarHome.php line 249
    OCA\DAV\CalDAV\CalDavBackend->createSubscription("*** sensitive parameters replaced ***")
16. /config/www/nextcloud/apps/dav/lib/CalDAV/CalendarHome.php line 93
    Sabre\CalDAV\CalendarHome->createExtendedCollection("*** sensitive parameters replaced ***")
17. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 1199
    OCA\DAV\CalDAV\CalendarHome->createExtendedCollection("*** sensitive parameters replaced ***")
18. /app/www/public/3rdparty/sabre/dav/lib/DAV/CorePlugin.php line 560
    Sabre\DAV\Server->createCollection("*** sensitive parameters replaced ***")
19. /app/www/public/3rdparty/sabre/event/lib/WildcardEmitterTrait.php line 89
    Sabre\DAV\CorePlugin->httpMkcol()
20. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 472
    Sabre\DAV\Server->emit()
21. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 253
    Sabre\DAV\Server->invokeMethod()
22. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 321
    Sabre\DAV\Server->start()
23. /config/www/nextcloud/apps/dav/lib/Server.php line 364
    Sabre\DAV\Server->exec()
24. /config/www/nextcloud/apps/dav/appinfo/v2/remote.php line 35
    OCA\DAV\Server->exec()
25. /app/www/public/remote.php line 172
    require_once("/config/www/nex ... p")

Caused by:

Doctrine\DBAL\Exception\DriverException: An exception occurred while executing a query: SQLSTATE[22007]: Invalid datetime format: 1366 Incorrect string value: '\xEBl Kee...' for column `nextcloud`.`oc_calendarobjects_props`.`value` at row 1 at <<closure>>

 0. /app/www/public/3rdparty/doctrine/dbal/src/Connection.php line 1814
    Doctrine\DBAL\Driver\API\MySQL\ExceptionConverter->convert()
 1. /app/www/public/3rdparty/doctrine/dbal/src/Connection.php line 1749
    Doctrine\DBAL\Connection->handleDriverException()
 2. /app/www/public/3rdparty/doctrine/dbal/src/Connection.php line 1163
    Doctrine\DBAL\Connection->convertExceptionDuringQuery()
 3. /app/www/public/lib/private/DB/Connection.php line 295
    Doctrine\DBAL\Connection->executeStatement()
 4. /app/www/public/3rdparty/doctrine/dbal/src/Query/QueryBuilder.php line 354
    OC\DB\Connection->executeStatement()
 5. /app/www/public/lib/private/DB/QueryBuilder/QueryBuilder.php line 280
    Doctrine\DBAL\Query\QueryBuilder->execute()
 6. /app/www/public/lib/private/DB/QueryBuilder/QueryBuilder.php line 326
    OC\DB\QueryBuilder\QueryBuilder->execute()
 7. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 2974
    OC\DB\QueryBuilder\QueryBuilder->executeStatement()
 8. /app/www/public/lib/public/AppFramework/Db/TTransactional.php line 63
    OCA\DAV\CalDAV\CalDavBackend->OCA\DAV\CalDAV\{closure}("*** sensitive parameters replaced ***")
 9. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 2932
    OCA\DAV\CalDAV\CalDavBackend->atomic()
10. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 1268
    OCA\DAV\CalDAV\CalDavBackend->updateProperties("*** sensitive parameters replaced ***")
11. /app/www/public/lib/public/AppFramework/Db/TTransactional.php line 63
    OCA\DAV\CalDAV\CalDavBackend->OCA\DAV\CalDAV\{closure}("*** sensitive parameters replaced ***")
12. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 1217
    OCA\DAV\CalDAV\CalDavBackend->atomic()
13. /config/www/nextcloud/apps/dav/lib/CalDAV/WebcalCaching/RefreshWebcalService.php line 129
    OCA\DAV\CalDAV\CalDavBackend->createCalendarObject("*** sensitive parameters replaced ***")
14. /config/www/nextcloud/apps/dav/lib/Listener/SubscriptionListener.php line 61
    OCA\DAV\CalDAV\WebcalCaching\RefreshWebcalService->refreshSubscription()
15. /app/www/public/lib/private/EventDispatcher/ServiceEventListener.php line 86
    OCA\DAV\Listener\SubscriptionListener->handle()
16. /app/www/public/3rdparty/symfony/event-dispatcher/EventDispatcher.php line 251
    OC\EventDispatcher\ServiceEventListener->__invoke()
17. /app/www/public/3rdparty/symfony/event-dispatcher/EventDispatcher.php line 73
    Symfony\Component\EventDispatcher\EventDispatcher->callListeners()
18. /app/www/public/lib/private/EventDispatcher/EventDispatcher.php line 87
    Symfony\Component\EventDispatcher\EventDispatcher->dispatch()
19. /app/www/public/lib/private/EventDispatcher/EventDispatcher.php line 99
    OC\EventDispatcher\EventDispatcher->dispatch()
20. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 2479
    OC\EventDispatcher\EventDispatcher->dispatchTyped()
21. /app/www/public/3rdparty/sabre/dav/lib/CalDAV/CalendarHome.php line 249
    OCA\DAV\CalDAV\CalDavBackend->createSubscription("*** sensitive parameters replaced ***")
22. /config/www/nextcloud/apps/dav/lib/CalDAV/CalendarHome.php line 93
    Sabre\CalDAV\CalendarHome->createExtendedCollection("*** sensitive parameters replaced ***")
23. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 1199
    OCA\DAV\CalDAV\CalendarHome->createExtendedCollection("*** sensitive parameters replaced ***")
24. /app/www/public/3rdparty/sabre/dav/lib/DAV/CorePlugin.php line 560
    Sabre\DAV\Server->createCollection("*** sensitive parameters replaced ***")
25. /app/www/public/3rdparty/sabre/event/lib/WildcardEmitterTrait.php line 89
    Sabre\DAV\CorePlugin->httpMkcol()
26. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 472
    Sabre\DAV\Server->emit()
27. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 253
    Sabre\DAV\Server->invokeMethod()
28. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 321
    Sabre\DAV\Server->start()
29. /config/www/nextcloud/apps/dav/lib/Server.php line 364
    Sabre\DAV\Server->exec()
30. /config/www/nextcloud/apps/dav/appinfo/v2/remote.php line 35
    OCA\DAV\Server->exec()
31. /app/www/public/remote.php line 172
    require_once("/config/www/nex ... p")

Caused by:

Doctrine\DBAL\Driver\PDO\Exception: SQLSTATE[22007]: Invalid datetime format: 1366 Incorrect string value: '\xEBl Kee...' for column `nextcloud`.`oc_calendarobjects_props`.`value` at row 1 at <<closure>>

 0. /app/www/public/3rdparty/doctrine/dbal/src/Driver/PDO/Statement.php line 103
    Doctrine\DBAL\Driver\PDO\Exception::new()
 1. /app/www/public/3rdparty/doctrine/dbal/src/Connection.php line 1153
    Doctrine\DBAL\Driver\PDO\Statement->execute()
 2. /app/www/public/lib/private/DB/Connection.php line 295
    Doctrine\DBAL\Connection->executeStatement()
 3. /app/www/public/3rdparty/doctrine/dbal/src/Query/QueryBuilder.php line 354
    OC\DB\Connection->executeStatement()
 4. /app/www/public/lib/private/DB/QueryBuilder/QueryBuilder.php line 280
    Doctrine\DBAL\Query\QueryBuilder->execute()
 5. /app/www/public/lib/private/DB/QueryBuilder/QueryBuilder.php line 326
    OC\DB\QueryBuilder\QueryBuilder->execute()
 6. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 2974
    OC\DB\QueryBuilder\QueryBuilder->executeStatement()
 7. /app/www/public/lib/public/AppFramework/Db/TTransactional.php line 63
    OCA\DAV\CalDAV\CalDavBackend->OCA\DAV\CalDAV\{closure}("*** sensitive parameters replaced ***")
 8. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 2932
    OCA\DAV\CalDAV\CalDavBackend->atomic()
 9. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 1268
    OCA\DAV\CalDAV\CalDavBackend->updateProperties("*** sensitive parameters replaced ***")
10. /app/www/public/lib/public/AppFramework/Db/TTransactional.php line 63
    OCA\DAV\CalDAV\CalDavBackend->OCA\DAV\CalDAV\{closure}("*** sensitive parameters replaced ***")
11. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 1217
    OCA\DAV\CalDAV\CalDavBackend->atomic()
12. /config/www/nextcloud/apps/dav/lib/CalDAV/WebcalCaching/RefreshWebcalService.php line 129
    OCA\DAV\CalDAV\CalDavBackend->createCalendarObject("*** sensitive parameters replaced ***")
13. /config/www/nextcloud/apps/dav/lib/Listener/SubscriptionListener.php line 61
    OCA\DAV\CalDAV\WebcalCaching\RefreshWebcalService->refreshSubscription()
14. /app/www/public/lib/private/EventDispatcher/ServiceEventListener.php line 86
    OCA\DAV\Listener\SubscriptionListener->handle()
15. /app/www/public/3rdparty/symfony/event-dispatcher/EventDispatcher.php line 251
    OC\EventDispatcher\ServiceEventListener->__invoke()
16. /app/www/public/3rdparty/symfony/event-dispatcher/EventDispatcher.php line 73
    Symfony\Component\EventDispatcher\EventDispatcher->callListeners()
17. /app/www/public/lib/private/EventDispatcher/EventDispatcher.php line 87
    Symfony\Component\EventDispatcher\EventDispatcher->dispatch()
18. /app/www/public/lib/private/EventDispatcher/EventDispatcher.php line 99
    OC\EventDispatcher\EventDispatcher->dispatch()
19. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 2479
    OC\EventDispatcher\EventDispatcher->dispatchTyped()
20. /app/www/public/3rdparty/sabre/dav/lib/CalDAV/CalendarHome.php line 249
    OCA\DAV\CalDAV\CalDavBackend->createSubscription("*** sensitive parameters replaced ***")
21. /config/www/nextcloud/apps/dav/lib/CalDAV/CalendarHome.php line 93
    Sabre\CalDAV\CalendarHome->createExtendedCollection("*** sensitive parameters replaced ***")
22. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 1199
    OCA\DAV\CalDAV\CalendarHome->createExtendedCollection("*** sensitive parameters replaced ***")
23. /app/www/public/3rdparty/sabre/dav/lib/DAV/CorePlugin.php line 560
    Sabre\DAV\Server->createCollection("*** sensitive parameters replaced ***")
24. /app/www/public/3rdparty/sabre/event/lib/WildcardEmitterTrait.php line 89
    Sabre\DAV\CorePlugin->httpMkcol()
25. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 472
    Sabre\DAV\Server->emit()
26. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 253
    Sabre\DAV\Server->invokeMethod()
27. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 321
    Sabre\DAV\Server->start()
28. /config/www/nextcloud/apps/dav/lib/Server.php line 364
    Sabre\DAV\Server->exec()
29. /config/www/nextcloud/apps/dav/appinfo/v2/remote.php line 35
    OCA\DAV\Server->exec()
30. /app/www/public/remote.php line 172
    require_once("/config/www/nex ... p")

Caused by:

PDOException: SQLSTATE[22007]: Invalid datetime format: 1366 Incorrect string value: '\xEBl Kee...' for column `nextcloud`.`oc_calendarobjects_props`.`value` at row 1 at <<closure>>

 0. /app/www/public/3rdparty/doctrine/dbal/src/Driver/PDO/Statement.php line 101
    PDOStatement->execute()
 1. /app/www/public/3rdparty/doctrine/dbal/src/Connection.php line 1153
    Doctrine\DBAL\Driver\PDO\Statement->execute()
 2. /app/www/public/lib/private/DB/Connection.php line 295
    Doctrine\DBAL\Connection->executeStatement()
 3. /app/www/public/3rdparty/doctrine/dbal/src/Query/QueryBuilder.php line 354
    OC\DB\Connection->executeStatement()
 4. /app/www/public/lib/private/DB/QueryBuilder/QueryBuilder.php line 280
    Doctrine\DBAL\Query\QueryBuilder->execute()
 5. /app/www/public/lib/private/DB/QueryBuilder/QueryBuilder.php line 326
    OC\DB\QueryBuilder\QueryBuilder->execute()
 6. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 2974
    OC\DB\QueryBuilder\QueryBuilder->executeStatement()
 7. /app/www/public/lib/public/AppFramework/Db/TTransactional.php line 63
    OCA\DAV\CalDAV\CalDavBackend->OCA\DAV\CalDAV\{closure}("*** sensitive parameters replaced ***")
 8. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 2932
    OCA\DAV\CalDAV\CalDavBackend->atomic()
 9. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 1268
    OCA\DAV\CalDAV\CalDavBackend->updateProperties("*** sensitive parameters replaced ***")
10. /app/www/public/lib/public/AppFramework/Db/TTransactional.php line 63
    OCA\DAV\CalDAV\CalDavBackend->OCA\DAV\CalDAV\{closure}("*** sensitive parameters replaced ***")
11. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 1217
    OCA\DAV\CalDAV\CalDavBackend->atomic()
12. /config/www/nextcloud/apps/dav/lib/CalDAV/WebcalCaching/RefreshWebcalService.php line 129
    OCA\DAV\CalDAV\CalDavBackend->createCalendarObject("*** sensitive parameters replaced ***")
13. /config/www/nextcloud/apps/dav/lib/Listener/SubscriptionListener.php line 61
    OCA\DAV\CalDAV\WebcalCaching\RefreshWebcalService->refreshSubscription()
14. /app/www/public/lib/private/EventDispatcher/ServiceEventListener.php line 86
    OCA\DAV\Listener\SubscriptionListener->handle()
15. /app/www/public/3rdparty/symfony/event-dispatcher/EventDispatcher.php line 251
    OC\EventDispatcher\ServiceEventListener->__invoke()
16. /app/www/public/3rdparty/symfony/event-dispatcher/EventDispatcher.php line 73
    Symfony\Component\EventDispatcher\EventDispatcher->callListeners()
17. /app/www/public/lib/private/EventDispatcher/EventDispatcher.php line 87
    Symfony\Component\EventDispatcher\EventDispatcher->dispatch()
18. /app/www/public/lib/private/EventDispatcher/EventDispatcher.php line 99
    OC\EventDispatcher\EventDispatcher->dispatch()
19. /config/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php line 2479
    OC\EventDispatcher\EventDispatcher->dispatchTyped()
20. /app/www/public/3rdparty/sabre/dav/lib/CalDAV/CalendarHome.php line 249
    OCA\DAV\CalDAV\CalDavBackend->createSubscription("*** sensitive parameters replaced ***")
21. /config/www/nextcloud/apps/dav/lib/CalDAV/CalendarHome.php line 93
    Sabre\CalDAV\CalendarHome->createExtendedCollection("*** sensitive parameters replaced ***")
22. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 1199
    OCA\DAV\CalDAV\CalendarHome->createExtendedCollection("*** sensitive parameters replaced ***")
23. /app/www/public/3rdparty/sabre/dav/lib/DAV/CorePlugin.php line 560
    Sabre\DAV\Server->createCollection("*** sensitive parameters replaced ***")
24. /app/www/public/3rdparty/sabre/event/lib/WildcardEmitterTrait.php line 89
    Sabre\DAV\CorePlugin->httpMkcol()
25. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 472
    Sabre\DAV\Server->emit()
26. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 253
    Sabre\DAV\Server->invokeMethod()
27. /app/www/public/3rdparty/sabre/dav/lib/DAV/Server.php line 321
    Sabre\DAV\Server->start()
28. /config/www/nextcloud/apps/dav/lib/Server.php line 364
    Sabre\DAV\Server->exec()
29. /config/www/nextcloud/apps/dav/appinfo/v2/remote.php line 35
    OCA\DAV\Server->exec()
30. /app/www/public/remote.php line 172
    require_once("/config/www/nex ... p")

MKCOL /remote.php/dav/calendars/admin/-
from 172.22.0.1 by admin at 2023-08-15T19:50:46+00:00

Additional info

I hope I gave all the necessary information.

Start in apps/dav/lib/CalDAV/CalDavBackend.php around line 2974 and trace the subscription refresh from RefreshWebcalService.php line 129. Reproduce the issue with a subscribed iCal event containing a non-ASCII character on MySQL or MariaDB, then verify that creating the subscription no longer fails and that the event data is handled as expected.