Codeigniter User Agent Not Working On Logout Controller - codeigniter

Question

In my MY_Controller.php I have a redirect in there if session has expired.
Then it redirects to the logout controller. I have added a if statement agent->is_referral to the logout controller and set flashdata. Because it has been redirect from dashboard controller it should pick up that if statement and set flashdata but does not.
Question: If the customer is redirected from whatever controller to logout then how to get is_referral() to detect and set the flashdata message. flashdata message is not setting when inside is_referral() if statement.
controllers > account > Logout.php
<?php
class Logout extends MY_Controller {
public function __construct() {
parent::__construct();
}
public function index() {
$this->load->library('user_agent');
if ($this->agent->is_referral()) {
// Does not set the flashdata if redirected from another controller.
$this->session->set_flashdata('warning', 'Your session has expired!');
}
// Flashdata works if have it here.
// $this->session->set_flashdata('warning', 'Your session has expired!');
$this->customer->logout();
redirect('/'); // redirect to login page.
}
}
core > MY_Controller.php
<?php
class MY_Controller extends CI_Controller {
public function __construct() {
parent::__construct();
if ($this->uri->segment(1)) {
if (!$this->session->userdata('customer_id')) {
$route = $this->uri->segment(1) .'/'. $this->uri->segment(2);
if (isset($route)) {
$ignore = array(
'account/logout'
);
if (!in_array($route, $ignore)) {
redirect('account/logout');
}
}
}
}
}
}
controllers > account > Dashboard.php
<?php
class Dashboard extends MY_Controller {
public function __construct() {
parent::__construct();
}
public function index() {
$this->load->view('common/header_view');
$this->load->view('account/dashboard_view');
$this->load->view('common/footer_view');
}
}