App restricted-to list keeps usergroups that no longer exist [NC 16.0.1]

[DBJRdev]

Steps to reproduce

1. Restrict any app to a specific user group.
2. Delete the user group in the user management.
3. The restricted-to list of the app still contains the non-existant group.

Expected behaviour

1. The app's restricted-to list should no longer contain a non-existant usergroup.
2. If it was the last group in the restricted-to list, then probably the app should be deactivated. (I was thinking about that for a while, but so far no better solution came to my mind.)

Actual behaviour

When installing a Nextcloud app, it is possible to restrict it to certain user groups. Yet after a group ceases to exit (=deleted in user management), the non-existant usergroup still appears in the restricted-to list of that app.

Server configuration

Operating system: Ubuntu (Shared hosting)

Web server: Apache

Database: MySQL

PHP version: 7.3

Nextcloud version: NC 16.0.1

Updated from an older Nextcloud/ownCloud or fresh install: upgrades since 12.x

Where did you install Nextcloud from: web installer

[violoncelloCH]

cc @nextcloud/server-triage

[MorrisJobke]

We might need to clean that up on group deletion. 🤔 (and add a repair job for existing ones)