check for bad xIntervals before multiply

Bug: oss-fuzz:6120
Change-Id: Icbd464352ad8ef1d35d274da049bc3424ccfa4d4
Reviewed-on: https://skia-review.googlesource.com/125420
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed