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: 843459f4

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



Change-Id: I09b97593299713b4f093e3ea0e56c7ebba26a29e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>