gltrace: Fix `passing NULL to non-pointer argument` warning.

Change-Id: I2f45db72912470e6ee22d0d64dc604c20524eabf
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/apitrace/+/2224525
Reviewed-by: Po-Hsien Wang <pwang@chromium.org>
Commit-Queue: Robert Tarasov <tutankhamen@chromium.org>
Tested-by: Robert Tarasov <tutankhamen@chromium.org>
1 file changed