The tests are failing after "Warning: incomplete system info collection"
which suggests systemInfo.gpus is empty. Check for that before indexing
into the vector; defaulting the active index to zero in
https://chromium-review.googlesource.com/c/angle/angle/+/1925031 was not
sufficient and the line still needs a bounds check.

Bug: chromium:923166, chromium:1032552
Change-Id: Ic9716830403e0dfcfa5d11539537c2a39e0e2386
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1959488Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Ian Elliott <ianelliott@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Ian Elliott <ianelliott@google.com>