I have a four page survery. I am using labels for the pages so they are all on the same timeline. When the user gets to the last page there is a submit button that sends all the variables to a php mailform file. However I keep getting TypeError: Error #1009: Cannot access a property or method of a null object reference. I dont think my variables are not being passed. What can I do?

Here is my code:

Code:
var variables:URLVariables = new URLVariables();
var varSend:URLRequest = new URLRequest("mailform.php");
var varLoader:URLLoader = new URLLoader;
varSend.method = URLRequestMethod.POST;
varSend.data = variables;

stop();

//sets focus to the Name text box
stage.focus = name_txt;


//handle events for buttons
form2.addEventListener(MouseEvent.CLICK,clickHandler);



function clickHandler(evtObj:MouseEvent){
	
	//validate form fields
	if(!name_txt.length) {
		results_txt.text = "Please enter your name.";	
	} else if(!email_txt.length) {
		results_txt.text = "Please enter an email address";
	}else if(!validateEmail(email_txt.text)) {
		results_txt.text = "Please enter a VALID email address";
	} else if(message_txt.length <= 1) {
		results_txt.text = "Please enter a message.";
	} else {
		
		trace("The " + evtObj.target.name + " button was clicked");
		gotoAndStop(evtObj.target.name)
	}
}


function validateEmail(str:String):Boolean {
	var pattern:RegExp = /(\w|[_.\-])+@((\w|-)+\.)+\w{2,4}+/;
	var result:Object = pattern.exec(str);
	if(result == null) {
		return false;
	}
	return true;
}


//function called from method, contains validation logic and var data to be sent to form
function sendData(event:MouseEvent):void{
	
   		variables.textName = name_txt.text;
   		variables.textEmail = email_txt.text;
   		variables.textMessage = message_txt.text;
		variables.textCompany = company_txt.text;
   		varLoader.load(varSend);
		
	
		trace("Email: "+email_txt.text);
		trace("Text length: "+message_txt.length);
		trace("Valid email: "+validateEmail(email_txt.text));
		trace("Message: "+message_txt.text);
		trace("Form validated");
		
	
	}