More polyutils fixes

Bug: chromium:954891, oss-fuzz:14079
Change-Id: Ia1ee0a15ab4bfc93e67188ff02e6aa436432a3be
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/211602
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
8 files changed