Fixed StreamingPlaybackService's query factory so it always returns

something. Returning null to callers is dangerous.

src/musikdroid/app/src/main/java/io/casey/musikcube/remote/playback/StreamingPlaybackService.java

@@ -871,7 +871,10 @@ public class StreamingPlaybackService implements PlaybackService {
                 }
             }
 
-            return null;
+            return SocketMessage.Builder
+                .request(Messages.Request.QueryTracks)
+                .addOption(Messages.Key.COUNT_ONLY, true)
+                .build();
         }
 
         @Override