Comment #7 on issue 2990 by [email protected]: \RemoveEmptyStaves in StaffGroup context crashes
http://code.google.com/p/lilypond/issues/detail?id=2990
So the right post-problem check would be not adding any VerticalAxisGroup to a VerticalAxisGroup. A more timely check would have the Axis_group_engraver barf when it wants to create a VerticalAxisGroup and there is already one visible in its context(?).
