Which Umbraco version are you using?

16.2.0-rc

Bug summary

When I try to remove the admin user group from a newly created user, I get an error notification with 'Admin User Group Must Not Be Empty'

This also occurs on 16.0.0

Specifics

Steps to reproduce

1. Create a new user with the admin user group
2. Go to the new user
3. Remove the admin user group
4. Click save
5. See error

Expected result / actual result

I would expect that the userGroup was removed without any errors