Menu Button Array - addChild Problem

1

hi. learning as3 and at a very basic level. i have changed my menu to an array and am having trouble with.

aboutus_btn
TypeError: Error #2007: Parameter child must be non-null.
	at flash.display::DisplayObjectContainer/addChild()
	at IndigoHair_fla::Content_1/goPage()

having no luck with getting rid of this error. any hints or help is much appreciated!

import flash.display.*;
import fl.transitions.*;
import fl.transitions.easing.*;

var home_btn:HomePage = new HomePage;
var aboutus_btn:AboutUsPage = new AboutUsPage;
var pricelist_btn:PricelistPage = new PricelistPage;
var products_btn:ProductsPage = new ProductsPage;
var promotions_btn:PromotionsPage = new PromotionsPage;
var theteam_btn:TheTeamPage = new TheTeamPage;
var contactus_btn:ContactUsPage = new ContactUsPage;
var media_btn:MediaPage = new MediaPage;
var jobs_btn:JobsPage = new JobsPage;
var events_btn:EventsPage = new EventsPage;

var TweenMenu:Tween = new Tween(mainmenubar_mc, "y", Elastic.easeOut, -600, 15, 2, true);
var TweenBackdrop:Tween = new Tween(backdrop_mc, "y", Elastic.easeOut, -650, 55, 2, true);
var TweenFooter:Tween = new Tween(footer_mc, "y", Elastic.easeOut, -600, 660, 2, true);

TweenMenu.addEventListener(TweenEvent.MOTION_FINISH, LoadContainer);
	function LoadContainer (event:TweenEvent):void {
		
		this.container_mc.addChild(home_btn);

		var TweenContainer:Tween = new Tween(container_mc, "y", Elastic.easeOut, -150, 55, 1.5, true);
	}
	
var buttonsArray:Array = new Array(mainmenubar_mc.home_btn, mainmenubar_mc.aboutus_btn, mainmenubar_mc.pricelist_btn, mainmenubar_mc.products_btn, mainmenubar_mc.promotions_btn, mainmenubar_mc.theteam_btn, mainmenubar_mc.contactus_btn);

for (var i:uint = 0; i < buttonsArray.length; i++) {
	
	buttonsArray*.addEventListener(MouseEvent.CLICK, goPage);
	
	function goPage(e:Event):void {
		trace(e.currentTarget.name)
		var Outro:Tween = new Tween(container_mc, "alpha", Strong.easeOut, 1, 0, 0.5, true);
		Outro.addEventListener(TweenEvent.MOTION_FINISH, PageTransition);
		function PageTransition (event:TweenEvent):void {
		this.container_mc.removeChildAt(0);
		this.container_mc.addChild(buttonsArray*);
		var Intro:Tween = new Tween(container_mc, "alpha", Strong.easeOut, 0, 1, 0.5, true);
		}
	}
}

regards Evo*