Group not fully removed from the web UI

[jvillafanez]

Steps to reproduce

1. Create a new group
2. Create a new user and add him to the group
3. Leave the group selector with that group
4. Delete the group from the web UI
5. Add a new user

At step 5, the user will have assigned the group that has been deleted at step 4. That group can't be changed. Creating the user will add the user to the group (the group will be created again), but the group won't be shown in the web UI.

Expected behaviour

The deleted group should be also removed from the selector regardless of being marked or not. That should solve the glitches described in this issue.

Actual behaviour

The web UI still has the group in the selector when a new user is created. This causes several UI problems

Server configuration

Operating system: ubuntu 20.04

Web server: apache 2.4

Database: mariaDB

PHP version: 7.4

ownCloud version: (see ownCloud admin page) checked with commit bda43ea (from #41077) . Likely reproducible with current master and 10.13.2

Updated from an older ownCloud or fresh install: fresh install

Where did you install ownCloud from:

Signing status (ownCloud 9.0 and above):

Login as admin user into your ownCloud and access 
http://example.com/index.php/settings/integrity/failed 
paste the results into https://gist.github.com/ and puth the link here.

The content of config/config.php:

Log in to the web-UI with an administrator account and click on
'admin' -> 'Generate Config Report' -> 'Download ownCloud config report'
This report includes the config.php settings, the list of activated apps
and other details in a well sanitized form.

or 

If you have access to your command line run e.g.:
sudo -u www-data php occ config:list system
from within your ownCloud installation folder

*ATTENTION:* Do not post your config.php file in public as is. Please use one of the above
methods whenever possible. Both, the generated reports from the web-ui and from occ config:list
consistently remove sensitive data. You still may want to review the report before sending.
If done manually then it is critical for your own privacy to dilligently
remove *all* host names, passwords, usernames, salts and other credentials before posting.
You should assume that attackers find such information and will use them against your systems.

List of activated apps:

If you have access to your command line run e.g.:
sudo -u www-data php occ app:list
from within your ownCloud installation folder.

Are you using external storage, if yes which one: local/smb/sftp/...

Are you using encryption: yes/no

Are you using an external user-backend, if yes which one: LDAP/ActiveDirectory/Webdav/...

LDAP configuration (delete this part if not used)

With access to your command line run e.g.:
sudo -u www-data php occ ldap:show-config
from within your ownCloud installation folder

Without access to your command line download the data/owncloud.db to your local
computer or access your SQL server remotely and run the select query:
SELECT * FROM `oc_appconfig` WHERE `appid` = 'user_ldap';


Eventually replace sensitive data as the name/IP-address of your LDAP server or groups.

Client configuration

Browser:

Operating system:

Logs

Web server error log

Insert your webserver log here

ownCloud log (data/owncloud.log)

Insert your ownCloud log here

Browser log

Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log 
c) ...