pip: Hide close and resize badges after dragging

DragDropAction changes the "reactive" property of the actors it handles.

Make the window reactive when drag & drop finishes.

Fix #1035

Author: JoseExposito

plugins/pip/PopupWindow.vala

@@ -200,6 +200,7 @@ public class Gala.Plugins.PIP.PopupWindow : Clutter.Actor {
     }
 
     private void on_move_end () {
+        reactive = true;
         update_screen_position ();
     }