Remove NPE inside WidgetsListAdapter during monkey actor test

b/22518383

Change-Id: I1a683c49be93af150f7873390b723cee0d4ac5df

src/com/android/launcher3/widget/WidgetsListAdapter.java

@@ -87,6 +87,9 @@ public class WidgetsListAdapter extends Adapter<WidgetsRowViewHolder> {
 
     @Override
     public int getItemCount() {
+        if (mWidgetsModel == null) {
+            return 0;
+        }
         return mWidgetsModel.getPackageSize();
     }