Do not crash when the resources are missing

In test_conversion_possible

BUG=skia:5314

Change-Id: Ia0e4178a262820b4161e55e07b0669f18322a64b
Reviewed-on: https://skia-review.googlesource.com/7742
Reviewed-by: Matt Sarett <msarett@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
1 file changed