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

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



Change-Id: I3eccad720748cf0f0bcd52a86c27fa6ef98e9630
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>