Merge "Null checking window before starting dream" into tm-qpr-dev am: 3ca388e8de am: 4ab949d7fa

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

Change-Id: I073a9241805877aa6886b75f0e51c84428deacc8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

core/java/android/service/dreams/DreamService.java

@@ -1409,6 +1409,10 @@ public class DreamService extends Service implements Window.Callback {
                             // Request the DreamOverlay be told to dream with dream's window
                             // parameters once the window has been attached.
                             mDreamStartOverlayConsumer = overlay -> {
+                                if (mWindow == null) {
+                                    Slog.d(TAG, "mWindow is null");
+                                    return;
+                                }
                                 try {
                                     overlay.startDream(mWindow.getAttributes(), mOverlayCallback,
                                             mDreamComponent.flattenToString(),