base

Fix crash on invalid dimlayer

If the app is already removed, don't apply any more dim on the window
that's pending removal. It causes invalid DimState to be added back
to the controller, and we crash as these don't have valid dimlayers.

bug: 25570092
Change-Id: I7e3c56c6eb636fdcb01d9bba90f77b3885e216fb