Update conversation-related strings

Test: atest
Bug: 157215227
Change-Id: Iba279bb285e53918a1e1b43c04d6ec7576cd48a0

src/com/android/settings/notification/app/NoConversationsPreferenceController.java

@@ -50,6 +50,11 @@ public class NoConversationsPreferenceController extends ConversationListPrefere
         return true;
     }
 
+    @Override
+    Preference getSummaryPreference() {
+        return null;
+    }
+
     @Override
     boolean matchesFilter(ConversationChannelWrapper conversation) {
         return false;