getDefaultHomeActivity() could return null ComponentName.

Bug: 153400018
Test: Manual test
Change-Id: I29d5a8f00563bdf88ab1f7a00d39d6a39a0ed44d

services/appwidget/java/com/android/server/appwidget/AppWidgetServiceImpl.java

@@ -3669,6 +3669,9 @@ class AppWidgetServiceImpl extends IAppWidgetService.Stub implements WidgetBacku
             // Default launcher from package manager.
             final ComponentName defaultLauncher = mPackageManagerInternal
                     .getDefaultHomeActivity(UserHandle.getUserId(callingUid));
+            if (defaultLauncher == null) {
+                return;
+            }
             int defaultLauncherUid  = 0;
             try {
                 defaultLauncherUid = mPackageManager.getApplicationInfo(