### Steps to reproduce

1. Be an admin

2. Go to the administration -> Work packages -> Priorities

3. Go to the priority that is currently the default one

4. Uncheck "active"

5. Save 


OR

1. Be an admin

2. Go to the administration -> Work packages -> Priorities

3. Go to the a currently inactive priority or turn one inactive

4. Check "default"

5. Begin of the insertionSaveEnd of the insertion Begin of the deletion Save End of the deletion


### What is the buggy behavior?

* Saving is possible without errors

* (potentially) being able to uncheck "active"  while also having the priority be the default one


### What is the expected behavior?

1. Either:

1. Saving an inactive default priority produces a visible error AND/OR

2. The UI prevents unchecking "Active" when "Default" is checked at the same time Begin of the deletion

1. Ideally, a caption explains that this combination is impossibleEnd of the deletion