[task driver] Fix nil-dereference in display
[task driver] Fix nil-dereference in display

Change-Id: I2d894a6a12245abfe4d1718663d4917660ca5c7b
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/298118
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot