Fix uninitialized variable in driver bug workaround. Bug: angleproject:4267 No-Try: True Change-Id: I5d9846779e4ac27313ec57b6ded935dbb40e1970 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1995829 Commit-Queue: Kenneth Russell <kbr@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>