Fix null pointer exception when surveys are turned off

In some conditions the survey provider could be null on
download completion which could lead to a NPE. This
has been addressed by not requiring an instance for
the removal of the receiver.

Test: RunSettingsRoboTests (master)
Bug: 33707203
Change-Id: Id1ab1a24c697fed8e4dd259682a088b50c35f38a
Merged-In: Icfb545697f24172db734dd7dad421796edf68186

src/com/android/settings/InstrumentedPreferenceFragment.java

@@ -66,9 +66,7 @@ public abstract class InstrumentedPreferenceFragment extends PreferenceFragment
     public void onPause() {
         Activity activity = getActivity();
         if (mReceiver != null && activity != null) {
-            SurveyFeatureProvider provider =
-                    FeatureFactory.getFactory(activity).getSurveyFeatureProvider(activity);
-            provider.unregisterReceiver(activity, mReceiver);
+            SurveyFeatureProvider.unregisterReceiver(activity, mReceiver);
             mReceiver = null;
         }