It -looks- like the undo action itself is the broken bit - which appears not to remove the object from the slide itself leaving it owned by the SfxListUndoAction and also linked to in the slide. Switching the master-page just clears the undo queue and forces the crash sooner (that would otherwise happen potentially much latter when it fell off the bottom of the undo queue). What a nice bug ! :-)
It -looks- like the undo action itself is the broken bit - which appears not to remove the object from the slide itself leaving it owned by the SfxListUndoAction and also linked to in the slide. Switching the master-page just clears the undo queue and forces the crash sooner (that would otherwise happen potentially much latter when it fell off the bottom of the undo queue). What a nice bug ! :-)