fix pathops fuzzes

Turn asserts into early exits.

R=kjlubick@google.com

Bug: skia:
Change-Id: I5da57e510774038f04381571aa2cebfbd26f03a1
Reviewed-on: https://skia-review.googlesource.com/c/171000
Commit-Queue: Cary Clark <caryclark@skia.org>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Auto-Submit: Cary Clark <caryclark@skia.org>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
2 files changed