TypeError: Error #1010: 条件は未定義であり、プロパティがありません。
	at MethodInfo-2()

package {
	import flash.events.MouseEvent;
	import flash.display.MovieClip;
	
	public class MouseEvents {
		var btn_mc1:MovieClip;

		public function MouseEvents(btn_mc1:MovieClip) {
			this.btn_mc1=btn_mc1;
			init();
		}

		private function init():void {
			btn_mc1.buttonMode=true;
			
			btn_mc1.addEventListener(MouseEvent.ROLL_OVER,myMouseEvent);

			function myMouseEvent (event:MouseEvent):void {
				this.btn_mc1.text1.gotoAndPlay("_frame2");
			}
		}
	}
}

var myMouseEvent:MouseEvents = new MouseEvents(btn_mc1);