detect overflow for morphology

Bug: oss-fuzz:8236
Change-Id: Iae911d995cbfed77c5d332f615da1a8d9b487c21
Reviewed-on: https://skia-review.googlesource.com/127703
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
2 files changed