ccpr: Fix a divide-by-zero in corner attenuation

Bug: skia:8098
Change-Id: I4ab1a9872a483b971b5e2e1903bf9ca61713eb01
Reviewed-on: https://skia-review.googlesource.com/c/159700
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
1 file changed