Associating the UIWindow with a different screen will trigger layout
of the child views of the window, including the view that we're in
the process of removing, which doesn't have a platform window anymore.
Instead of protecting every possible code path in the view code
with checks for a platform window we defer the restoring of
mirror mode until after the view has been removed.
Pick-to: 6.2 5.15
Task-number: QTBUG-94530
Change-Id: I8c66106cafa67e06721e621c019b2d10acf02326
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
36852d78bf