conic fuzz fix

If no closest section is found in conic intersection
(which can happen if the numbers are out of range)
abort the intersection.

Also suppress assert fired in this case so it only
checks intersections with in-range values.

TBR=reed@google.com
BUG=630378
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2166813006

Review-Url: https://codereview.chromium.org/2166813006
3 files changed