Fix warnings produced from MSVS code analysis. 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>