Merge "Check the nullity of display when remove starting window" into udc-dev...

Merge "Check the nullity of display when remove starting window" into udc-dev am: aca03f82 am: 0f287c82

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/22679890



Change-Id: I42a6a93450c931c01e6a320ac263631712b30be7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>