If there is only one admin user, this admin cannot change the role of non-admin users to admin

[texnixe]

Describe the bug
As it says in the title.

To Reproduce
Steps to reproduce the behavior:

1. Create a new user role, e.g. client.
2. Create a user with this role.
3. Then, try to change the role of this user to admin.
4. The changeRole dialog in this case doesn't offer any other roles to change to apart from the current role.

Expected behavior
It should be possible to change the role of an existing user to admin.

Additional context
Note that it is possible to create new admin users. It is also possible to change the role of a non-admin user to admin if you create a second admin user first.

Kirby Version
Tested with 3.2.2

[bastianallgeier]

✅