Fix sketchy usage of new PreferenceScreen

Things get weird if you don't use PreferenceManager#createPreferenceScreen

Bug: 37216851
Test: Compiles and runs
Change-Id: I7cebec133c4f27f7eeda83c95d8acb4823f67dc4

src/com/android/settings/ApnSettings.java

@@ -184,8 +184,7 @@ public class ApnSettings extends RestrictedSettingsFragment implements
         mUnavailable = isUiRestricted();
         setHasOptionsMenu(!mUnavailable);
         if (mUnavailable) {
-            setPreferenceScreen(new PreferenceScreen(getPrefContext(), null));
-            getPreferenceScreen().removeAll();
+            addPreferencesFromResource(R.xml.empty_settings);
             return;
         }