Creating directory in groupfolder fails with more than one group assigned

[aleadco]

Description

After upgrading to NC21.01 there are errors in creating and deleting folders in groups with more than one group assigned.

Steps to reproduce

1. Create group folder and authorize only one group at first.
2. Create content within the folder, it will not be a problem now.
3. Authorize a second group to access the group folder. At this point, when you try to create a folder it says that it could not be created and the same happens if you want to delete something that is already created.

Expected behaviour

Tell us what should happen

Actual behaviour

Tell us what happens instead

Server configuration

**Operating system:**Ubuntu 18.04

**Web server:**Apache2 FPM

**Database:**MySQL 8.0

**PHP version:**8

Nextcloud version: 21.01

**Updated from an older Nextcloud/ownCloud or fresh install:**No

**Where did you install Nextcloud from:**tar

[ghost]

here also. Maybe the same / related to #1455, #1456

[ghost]

Can this error from the logs have anything to do with this issue?
Edit: reported as https://github.com/nextcloud/server/issues/26746

Error | TypeError: Unsupported operand types: int & array

/var/www/nextcloud/lib/private/Files/Cache/Wrapper/CacheWrapper.php - line 74:OC\Files\Cache\Wrapper\CachePermissionsMask->formatCacheEntry()

/var/www/nextcloud/apps/groupfolders/lib/Versions/VersionsBackend.php - line 170:OC\Files\Cache\Wrapper\CacheWrapper->get()

<<closure>>OCA\GroupFolders\Versions\VersionsBackend->OCA\GroupFolders\Versions\{closure}("*** sensiti ... *")

/var/www/nextcloud/apps/groupfolders/lib/Versions/VersionsBackend.php - line 169:array_map()

/var/www/nextcloud/apps/groupfolders/lib/Versions/GroupVersionsExpireManager.php - line 64:OCA\GroupFolders\Versions\VersionsBackend->getAllVersionedFiles()

/var/www/nextcloud/apps/groupfolders/lib/Versions/GroupVersionsExpireManager.php - line 58:OCA\GroupFolders\Versions\GroupVersionsExpireManager->expireFolder()

/var/www/nextcloud/apps/groupfolders/lib/BackgroundJob/ExpireGroupVersions.php - line 40:OCA\GroupFolders\Versions\GroupVersionsExpireManager->expireAll()

/var/www/nextcloud/lib/private/BackgroundJob/Job.php - line 52:OCA\GroupFolders\BackgroundJob\ExpireGroupVersions->run()

 /var/www/nextcloud/lib/private/BackgroundJob/TimedJob.php - line 59:OC\BackgroundJob\Job->execute()

/var/www/nextcloud/cron.php - line 128:OC\BackgroundJob\TimedJob->execute() 

[joshtrichards]

Unable to reproduce today. And this report hasn't seen any traffic >3 years. Presumed fixed.