handle empty contours in a couple more places

R=kjlubick@google.com
BUG=skia:6061

Change-Id: I5b465f1495f80a5ac44253cadf4afd7f509fa75b
Reviewed-on: https://skia-review.googlesource.com/6268
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Cary Clark <caryclark@google.com>
1 file changed