Avoid stripping empty screens if the workspace is still loading (issue 12523285)

-> This appears to be what may be causing data loss in some users during update.
   A certain (seemingly) rare combination of life-cycle events and package events
   seems to be the culprit (potentially why it's seen at update time).

Change-Id: Iea4f8aef012ba80b7ba568e0df264edb9284efbe