fix fuzz

Don't walk off the end if the loop doesn't
contain the expected value.

R=kjlubick@google.com
BUG=skia:6047

Change-Id: I96815180dc7c92b45691037ae6c4b40beedc009a
Reviewed-on: https://skia-review.googlesource.com/5845
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Cary Clark <caryclark@google.com>
1 file changed