No error message shown when bulk editing members with users who are no longer members of the room

[Sabr1n4W]

Describe the bug When bulk editing member roles of room members there is no error message shown when the request failes because one of the users is no longer a member of the room.

To Reproduce Steps to reproduce the behavior:

1. Open a room with one ore more members
2. Select all users and open the bulk edit dialog and select a role
3. Delete one of the room members in another tab
4. Now try to edit the room members with the open bulk edit dialog
5. The request will fail with a 422 error but no error message is shown in the dialog

Expected behavior Display an error message inside the dialog after the request failed

Additional context An alternative solution would be to give the user trying to bulk edit the members the option to only bulk edit the existing users after the error occured.