[Bug #1297] Reset the list listenersToAdd when changing perspectives.

Not resetting it keeps the old listeners attached to the resources/criteria
selector and name filter.

FEA: ItEr75S04BugFixing

libreplan-webapp/src/main/java/org/libreplan/web/resourceload/ResourceLoadController.java

@@ -192,6 +192,7 @@ public class ResourceLoadController implements Composer {
             resourcesLoadPanel = null;
             listeners = new ListenerTracker();
             visualizationModifiers = null;
+            listenersToAdd = null;
         }
 
         public IOnTransaction<Void> reload() {