PureMVC, register popup mediator problem

Below is my code for popup, in my project, I have a problem to register mediator, I try like this ::  facade.registerMediator(new InfoWindowFriendDetailsMediator(InfoWindowFriendDetails));  ::

Problem happened when I register events on my popup component controls, I get null here and application crash. I don't know how to register mediator?

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override public function onRegister():void
                {
                        friendDetailsInfoWindow.btnCloseInfoWindowFriendDetails.addEventListener(MouseEvent.CLICK, onCloseClick);
                }

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package util.popup
{
        import flash.display.DisplayObject;
        import flash.display.Sprite;

        import mx.core.Application;
        import mx.core.IFlexDisplayObject;
        import mx.managers.PopUpManager;

        import org.puremvc.as3.multicore.patterns.facade.Facade;

        /**
         * Used to handle popup opening controling registering and unregistering mediators
         *
         * @author
         */

        public class PopManager extends PopUpManager
        {
                private static var popupList:Array=new Array();

                /**
                 * Opens a popup window. Window component is crated and mediator is assigned to it.
                 * Targeted for PureMVC multicore so method requires moduleId to be passed
                 */
                public static function openPopUpWindow(ComponentClass:Class, MediatorClass:Class, moduleUid:String, modal:Boolean=true, parent:DisplayObject=null):IFlexDisplayObject
                {
                        if (parent == null)
                        {
                                parent=Application.application as DisplayObject;
                        }
                        var window:IFlexDisplayObject=PopUpManager.createPopUp(parent, ComponentClass, modal);
                        var obj:Facade=Facade.getInstance(moduleUid)as Facade;

                        obj.registerMediator(new MediatorClass(window));
                        PopUpManager.centerPopUp(window);
                        return window;
                }

                /**
                 *  Removes PopUp window and unregisteres associated mediator
                 */
                public static function closePopUpWindow(window:IFlexDisplayObject, mediatorName:String, moduleUid:String):void
                {
                        PopUpManager.removePopUp(window);
                        Facade.getInstance(moduleUid).removeMediator(mediatorName);
                }

                /**
                 *
                 * Tries to retrieve popup window from the list of popups already opened. If there is no window opened with
                 * provided mediator name associated with it, a new one is created and displayed.
                 */
                public static function retrievePopUp(ComponentClass:Class, MediatorClass:Class, mediatorName:String, moduleUid:String, modal:Boolean=true):IFlexDisplayObject
                {
                        if (popupList[mediatorName])
                        {
                                PopUpManager.addPopUp(popupList[mediatorName]as IFlexDisplayObject, Application.application as Sprite, modal);
                                PopUpManager.bringToFront(popupList[mediatorName]);
                        }
                        else
                        {
                                popupList[mediatorName]=openPopUpWindow(ComponentClass, MediatorClass, moduleUid, modal)
                        }
                        return popupList[mediatorName];
                }

                /**
                 *  Removes popup from display list. The actual popup object still exists in the list and can be retrieved
                 */
                public static function hidePopUp(window:IFlexDisplayObject, mediatorName:String):void
                {
                        PopUpManager.removePopUp(window);
                }

                /**
                 * Removes the popup completle. Also unregisters mediator.
                 */
                public static function destroyPopUp(window:IFlexDisplayObject, mediatorName:String, moduleUid:String):void
                {
                        closePopUpWindow(window, mediatorName, moduleUid);

                        if (popupList[mediatorName])
                        {
                                popupList[mediatorName]=null;
                        }
                }
        }


}