DrmHalTest: null check for skipped test am: 9049fc93a8 am: efe8d1a7a4

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2417394

Change-Id: I885e3f4829b72bf8ba4e7d99dad0c85a06f3b465
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>