Fixes: NB#274133 - No content (black screen) when systemwide sheet is closing before the end of his sliding animation - possiblyUnredirectTopmostWindow(): if VKB is on top, check if its transient   parent is closing
Fixes: NB#274133 - No content (black screen) when systemwide sheet is closing before the end of his sliding animation
- possiblyUnredirectTopmostWindow(): if VKB is on top, check if its transient
  parent is closing

nemomobile-graveyard/mcompositor,nemomobile-graveyard/mcompositor,nemomobile-graveyard/mcompositor,nemomobile-graveyard/mcompositor,nemomobile-graveyard/mcompositor,nemomobile-graveyard/mcompositor