Here is registerController.php
$query = "SELECT email FROM {{tokens_$surveyid}}\n"
. "WHERE email = '".sanitize_email(Yii::app()->request->getPost('register_email'))."'";
//$result = dbExecuteAssoc($query) or show_error("Unable to execute this query : \n <br />".$query."<br />"); //Checked)
$result = dbExecuteAssoc($query) or safe_die ($query."".$connect->ErrorMsg());
if (($result->count()) > 0)
{
$register_errormsg = $clang->gT("The email you used has already been registered.");
$SESSION['survey'.$surveyid]['register_errormsg']=$register_errormsg;

         Yii::app()->request->redirect(Yii::app()->createUrl('survey/index/sid/'.$surveyid));
       /* include "index.php";
        exit;*/

The email you used has already been registered. is not appearing on my site