Adding check for no default home before registering new receiver

Bug: 135473571
Test: Manual, try restarting with no default launcher set?
Change-Id: Ibb68070ee95ca856b38a74823bcbfbc7890f329e
diff --git a/quickstep/src/com/android/quickstep/OverviewComponentObserver.java b/quickstep/src/com/android/quickstep/OverviewComponentObserver.java
index b5da836..0a73b8b 100644
--- a/quickstep/src/com/android/quickstep/OverviewComponentObserver.java
+++ b/quickstep/src/com/android/quickstep/OverviewComponentObserver.java
@@ -115,7 +115,11 @@
             // as uninstalling the app or removing the "Launcher" feature in an update).
             // Listen for package updates of this app (and remove any previously attached
             // package listener).
-            if (!defaultHome.getPackageName().equals(mUpdateRegisteredPackage)) {
+            if (defaultHome == null) {
+                if (mUpdateRegisteredPackage != null) {
+                    mContext.unregisterReceiver(mOtherHomeAppUpdateReceiver);
+                }
+            } else if (!defaultHome.getPackageName().equals(mUpdateRegisteredPackage)) {
                 if (mUpdateRegisteredPackage != null) {
                     mContext.unregisterReceiver(mOtherHomeAppUpdateReceiver);
                 }