Clean code

app/src/mobile/java/com/fongmi/android/tv/utils/ScanTask.java

@@ -35,10 +35,10 @@ public class ScanTask {
     }
 
     public void stop() {
-        future.forEach(f -> f.cancel(true));
+        listener = null;
         OkHttp.cancel(client, "scan");
+        future.forEach(f -> f.cancel(true));
         future.clear();
-        listener = null;
     }
 
     private void run(List<String> urls) {