DrmHalTest: null check for skipped test am: 9049fc93a8 am: efe8d1a7a4 am: 652101329e

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

Change-Id: Icb3e5479596b1dd1baa4505282f03dc4833ad83b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>