Try updating line 14 to:
$WAFV_Errors .= WAValidateLE((strtolower(isset($_POST["fieldset_group_4_Security_Question_2"])?$_POST["fieldset_group_4_Security_Question_2"]:"")) . "",((isset($_SESSION["random_answer"]))?strtolower($_SESSION["random_answer"]):"") . "",true,4);
it looks like the session variable reference is wrong currently. I'll have to look into why that would happen.