Errors on delete groups

[jzawer]

Steps to reproduce

1. Login as Administrator.
2. Go to Users.
3. On left panel, delete a group.
4. In user list, when you try to change the user group, you can add the deleted group.
5. Errors appears but you see the deleted group as marked.

Expected behaviour

When a group is deleted, the list of groups in user list should be refreshed.

Actual behaviour

When you delete one group, the list of groups in user list doesn't refresh and admin can mark deleted group in user and get errors.

Server configuration.

Nextcloud version: 12