Merge "Null checking window before starting dream" into tm-qpr-dev am:...

Merge "Null checking window before starting dream" into tm-qpr-dev am: 3ca388e8 am: 4ab949d7 am: f538befc

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/21798643



Change-Id: Icffcc24be4bb93f22c8da305f02aa0752e3b5d23
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>