Error #1010: A term is undefined and has no properties

Question

i tried making a button that makes it go to the next frame but when i tried it there was an output that said "TypeError: Error #1010: A term is undefined and has no properties." i tried to find any script errors but cant find any, heres the script

stop();
this.nextbutton.addEventListener(MouseEvent.CLICK, click);

function click(e:MouseEvent):void
{
    nextFrame();
}

this was my first time trying to do actionscript3