We could dereference a null pointer in a couple edge cases.

BUG=angleproject:2151

Change-Id: I0d40b930c5008b80928bfe8c93588f80127fd166
Reviewed-on: https://chromium-review.googlesource.com/665995
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>