Merge "Guard potential null case in FullscreenTaskListener.releaseWindowDecor found in testing." into tm-qpr-dev am: 21688acee8 am: 016b26accb

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/19794348

Change-Id: I86872d368f665864318ea551eec6812ea9fd26c2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>