[Bug]: User is shown alway busy after set Availability once

⚠️ 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 set once, remove all the time slots is displayed as "never at office" in the free busy calendar.

Steps to reproduce

1. create a new user and use
2. look in the free/busy calendar : the user is free
3. add one working time slot and apply
4. remove the time slot and apply
5. look in the free/busy calendar : the user is busy

Expected behavior

short

The state should come back at the previous know state if we revert our changes.
So : free before set/remove time slot, free after

long

• Allow to enable/disable the Availability feature
• when disabled, allow to choose if shown free or busy

Installation method

Community Manual installation with Archive

Nextcloud Server version

28

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.2

Web server

Nginx

Database engine version

MySQL

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

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

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

Configuration report

No response

List of activated Apps

No response

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

No files, tests, or entry points are named. Reproduce the five listed availability steps on Nextcloud Server 28, then locate the availability and free/busy implementation through the project search; done means removing the only time slot restores the user's previous free state. Treat the enable/disable and default-status requests as broader follow-up scope.