Handle possible degenerate case in the hairline path renderer

Bug:1172796
Change-Id: Ifc03709a0f978b4dec6c8f7ea2c721c860167abb
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/366337
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
1 file changed