Steps:

1. Add Cube to the Hierarchy
2. Make a prefab put of it
3. Select Cube Instance in the Hierarchy
4. Remove BoxCollider
5. Choose "RemovedComponent => Apply to prefab" context menu item
==>
"Nothing selected" is still shown in the Inspector

Note:
1. Changing selection and then back to the instance will clear the "Nothing selected" thing
2. Appears after the fix of the https://fogbugz.unity3d.com/f/cases/1102102