TypeError: Error #1009 issue throughout

Hi,

I'm having this issue throughout my program. I'm not well versed in Flash. Here's the code:

import flash.events.MouseEvent;

stop();

emer_cont_btn.enabled = true;

emer_exit_btn.enabled = true;

emer_help_btn.enabled = true;

emer_glossary_btn.enabled = true;

emer_mm_btn.enabled = true;

emer_btn.enabled = true;

emer_cont_btn.addEventListener(MouseEvent.CLICK, Cont2e);

function Cont2e(event:MouseEvent):void

{

          emerstory01.stop();

          gotoAndStop("3E");

}

emer_btn.addEventListener(MouseEvent.CLICK, Emer2e);

function Emer2e(event:MouseEvent):void

{

          emerstory01.stop();

          gotoAndStop("1E","Emer");

}

emer_exit_btn.addEventListener(MouseEvent.CLICK, Scene2e);

function Scene2e(event:MouseEvent):void

{

          emerstory01.stop();

          gotoAndStop("one","Scene2");

}

emer_mm_btn.addEventListener(MouseEvent.CLICK, MainMenu2e);

function MainMenu2e(event:MouseEvent):void

{

          emerstory01.stop();

          gotoAndStop("onea","MainMenu");

}

emer_help_btn.addEventListener(MouseEvent.CLICK, Help2e);

function Help2e(event:MouseEvent):void

{

          emerstory01.stop();

          gotoAndStop("oneb","Help");

}

emer_glossary_btn.addEventListener(MouseEvent.CLICK, Glossary2e);

function Glossary2e(event:MouseEvent):void

{

          emerstory01.stop();

          gotoAndStop("onec","Glossary");

}

I'm pulling the video from an external source and when I click continue the video doesn't stop and keeps playing. Is there a way to write this so that no matter what link/button I click the video stops playing?? I will need to do this throughout my program it seems so any help would be amazing!!!

Here's the errors I got for this output:

TypeError: Error #1009: Cannot access a property or method of a null object reference.

          at MySafeSchool_fla::MainTimeline/Emer2e()

TypeError: Error #1009: Cannot access a property or method of a null object reference.

          at MySafeSchool_fla::MainTimeline/Cont2e()