Screenshots can be corrupted by reordering VPL code

Created by: ddoak

See these example screenshots:

and

To reproduce: Create a VPL program with instruction lines of different lengths (e.g. 1 vs 2 action blocks). Save a screenshot of the program, then reorder the instruction lines by dragging one on top of the other and then screenshot again. The second screenshot will contain un-refreshed areas where the graphics did not overlap.

Only tested so far on Mac (OS X 10.9.5) (100% reproducible on two different machines)