TypeError A term is undefined and has no properties

Hello again sorry for coming back so early but i have this error

if (objMode == null) {
objMode = new battle_mode_mc;
mSystem.contMENU2.addChild(objMode);
objMode.btn_insane.addEventListener(MouseEvent.CLICK, modeInsaneClick, false, 0, true);      <--- this is the line it says is undefined and has no properties
///
objMode.btn_insane.visible = false;
///
_area_select = AREA;
_battle_mode = 1;

private function modeInsaneClick(event:MouseEvent):void {
_battle_mode = 4;
var clip = new battle_mc;
clip.init(mSystem, _area_select, _battle_mode);
destroy();

}