This would cause internal errors to trigger a nullptr dereference.
Bug introduced in "Add gl::ErrorSet and angle::Result." 6b873dd7

Bug: angleproject:2491
Change-Id: Ia98d59d27614912631d41ff0823ee5aa50769733
Reviewed-on: https://chromium-review.googlesource.com/1138408Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>