Fix crash when there is no emergencybroadcast app on device

Some devices do not have emergencybroadcast app installed, so we should
not show the preference item for it. Add the preference controller into
AppAndNotificationFragment properly hides it.

Change-Id: Ic39ba24da9bd8f3200a5e44232a5489e35c48c0a
Fix: 37945069
Test: make RunSettingsRoboTests

src/com/android/settings/applications/AppAndNotificationDashboardFragment.java

@@ -23,6 +23,7 @@ import com.android.internal.logging.nano.MetricsProto;
 import com.android.settings.R;
 import com.android.settings.core.PreferenceController;
 import com.android.settings.dashboard.DashboardFragment;
+import com.android.settings.notification.EmergencyBroadcastPreferenceController;
 import com.android.settings.search.BaseSearchIndexProvider;
 
 import java.util.ArrayList;
@@ -61,6 +62,8 @@ public class AppAndNotificationDashboardFragment extends DashboardFragment {
 
     private static List<PreferenceController> buildPreferenceControllers(Context context) {
         final List<PreferenceController> controllers = new ArrayList<>();
+        controllers.add(new EmergencyBroadcastPreferenceController(context,
+                "app_and_notif_cell_broadcast_settings"));
         controllers.add(new SpecialAppAccessPreferenceController(context));
         return controllers;
     }