Hide Display Theme from search results when not available

Test: make RunSettingsRoboTests
Fixes: 62377986
Change-Id: I5d0737034ef3f845e790934465b65a5415654822

src/com/android/settings/DisplaySettings.java

@@ -129,7 +129,7 @@ public class DisplaySettings extends DashboardFragment {
 
                 @Override
                 public List<String> getNonIndexableKeys(Context context) {
-                    List<String> keys = new ArrayList<>();
+                    List<String> keys = super.getNonIndexableKeys(context);
                     keys.add(KEY_DISPLAY_SIZE);
                     return keys;
                 }