[Bug]: ShareApiController currentuser property type issue

⚠️ 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

In
https://github.com/nextcloud/server/blob/master/apps/files_sharing/lib/Controller/ShareAPIController.php#L63C2-L63C30
the currentUser property is typed as string, but in constructor the parameter is signed as ?string $userId = null , so in some circumstances there is this error:
Exception":"TypeError, Cannot assign null to property OCA\\Files_Sharing\\Controller\\ShareAPIController::$currentUser of type string

Steps to reproduce

1. It happens when share api is used via webapppassword in nc 29

Expected behavior

Allow userId to be null when using createShare method setting the property type the same as the parameter type.

Installation method

None

Nextcloud Server version

29

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

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

{
  "reqId": "2M3DAMpzQRlKeiad9X2L",
  "level": 3,
  "time": "2024-06-24T18:22:46+00:00",
  "remoteAddr": "188.77.44.131",
  "user": "--",
  "app": "index",
  "method": "OPTIONS",
  "url": "/index.php/apps/webapppassword/api/v1/shares",
  "message": "Cannot assign null to property OCA\\Files_Sharing\\Controller\\ShareAPIController::$currentUser of type string",
  "userAgent": "Mozilla/5.0 (X11; Linux x86_64; rv:128.0) Gecko/20100101 Firefox/128.0",
  "version": "29.0.2.2",
  "exception": {
    "Exception": "TypeError",
    "Message": "Cannot assign null to property OCA\\Files_Sharing\\Controller\\ShareAPIController::$currentUser of type string",
    "Code": 0,
    "Trace": [
      {
        "function": "__construct",
        "class": "OCA\\Files_Sharing\\Controller\\ShareAPIController",
        "type": "->"
      },
      {
        "file": "web/lib/private/AppFramework/Utility/SimpleContainer.php",
        "line": 83,
        "function": "newInstanceArgs",
        "class": "ReflectionClass",
        "type": "->"
      },
      {
        "file": "web/lib/private/AppFramework/Utility/SimpleContainer.php",
        "line": 128,
        "function": "buildClass",
        "class": "OC\\AppFramework\\Utility\\SimpleContainer",
        "type": "->"
      },
      {
        "file": "web/lib/private/AppFramework/Utility/SimpleContainer.php",
        "line": 146,
        "function": "resolve",
        "class": "OC\\AppFramework\\Utility\\SimpleContainer",
        "type": "->"
      },
      {
        "file": "web/lib/private/AppFramework/DependencyInjection/DIContainer.php",
        "line": 470,
        "function": "query",
        "class": "OC\\AppFramework\\Utility\\SimpleContainer",
        "type": "->"
      },
      {
        "file": "web/lib/private/AppFramework/DependencyInjection/DIContainer.php",
        "line": 442,
        "function": "queryNoFallback",
        "class": "OC\\AppFramework\\DependencyInjection\\DIContainer",
        "type": "->"
      },
      {
        "file": "web/lib/private/AppFramework/App.php",
        "line": 163,
        "function": "query",
        "class": "OC\\AppFramework\\DependencyInjection\\DIContainer",
        "type": "->"
      },
      {
        "file": "web/lib/private/Route/Router.php",
        "line": 338,
        "function": "main",
        "class": "OC\\AppFramework\\App",
        "type": "::"
      },
      {
        "file": "web/lib/base.php",
        "line": 1050,
        "function": "match",
        "class": "OC\\Route\\Router",
        "type": "->"
      },
      {
        "file": "web/index.php",
        "line": 49,
        "function": "handleRequest",
        "class": "OC",
        "type": "::"
      }
    ],
    "File": "web/apps/files_sharing/lib/Controller/ShareAPIController.php",
    "Line": 124,
    "message": "Cannot assign null to property OCA\\Files_Sharing\\Controller\\ShareAPIController::$currentUser of type string",
    "exception": {},
    "CustomMessage": "Cannot assign null to property OCA\\Files_Sharing\\Controller\\ShareAPIController::$currentUser of type string"
  }
}

Additional info

No response

Open apps/files_sharing/lib/Controller/ShareAPIController.php and inspect the currentUser property near line 63 and the constructor near line 124. Reproduce or review the webapppassword share API path that supplies a null userId. Done means the controller no longer raises the reported TypeError when createShare is used with that path, with relevant tests or checks passing.