Fix a NPE where developer options page crash sometimes.

Developer options page crash for restricted users because the page
removes all preferences while DashboardFeatureProvider tries to
manipulate preferences on screen.

Added a null check to skip changin prefs in DashboardFeatureProvider
because the pref is going to be removed either way.

Change-Id: Ic83fd0dfb2a906605fb1d992d7b36c2163630e89
Fixes: 78655710
Test: robotests

tests/robotests/src/com/android/settings/dashboard/DashboardFeatureProviderImplTest.java

@@ -24,6 +24,7 @@ import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyZeroInteractions;
 import static org.mockito.Mockito.when;
 import static org.robolectric.Shadows.shadowOf;
 
@@ -214,6 +215,15 @@ public class DashboardFeatureProviderImplTest {
                 .startActivityForResultAsUser(any(Intent.class), anyInt(), any(UserHandle.class));
     }
 
+    @Test
+    public void bindPreference_nullPreference_shouldIgnore() {
+        final Tile tile = mock(Tile.class);
+        mImpl.bindPreferenceToTile(mActivity, MetricsProto.MetricsEvent.VIEW_UNKNOWN,
+                null, tile, "123", Preference.DEFAULT_ORDER);
+
+        verifyZeroInteractions(tile);
+    }
+
     @Test
     public void bindPreference_withNullKeyNullPriority_shouldGenerateKeyAndPriority() {
         final Preference preference = new Preference(RuntimeEnvironment.application);