Fix a crash in the clockwise gm

Bug: skia:
Change-Id: Idc441d15bb03ef57ba82bb59249cce0c220c0488
Reviewed-on: https://skia-review.googlesource.com/144141
Reviewed-by: Ben Wagner <benjaminwagner@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
1 file changed