In some code path found by a fuzzer, we would have a zero sized
array, which would trigger a zero divide. I was unable to extract
the failing shader from the fuzzer case trivially.

BUG=chromium:653274

Change-Id: Ia2558ae828fa73615c901fd1cda9ddaa3a72f1a9
Reviewed-on: https://chromium-review.googlesource.com/394238Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>