Merge "WallpaperManagerService:fix potential null pointer exception in onDisplayRemoved method." into main am: a5cab7b8dc

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/3133377

Change-Id: I74aeff1507bbad18c0198cbea07a6b9de3cc8481
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>