Hmvc personal module error

Hi, i need to create a different 404 error page forn all modules folders
ex.
modules
-> frontend
-> errors
-> error_404.php
-> backend
-> errors
-> error_404.php

I create MY_Exceptions.php on application/core/ with this code:
<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
require APPPATH."third_party/MX/Exceptions.php";
class MY_Exceptions extends MX_Exceptions {}
?>

and Exceptions.php on application/third_party/MX:

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class MX_Exceptions extends CI_Exceptions {

function show_404($page = '', $log_error = TRUE)
{

$heading = "404 Page Not Found";
$message = "The page you requested was not found.";

// By default we log this, but allow a dev to skip it
if ($log_error)
{
log_message('error', '404 Page Not Found --> '.$page);
}

echo $this->show_error($heading, $message, 'error_404', 404);
exit;
}

// --------------------------------------------------------------------

/**
* General Error Page
*
* This function takes an error message as input
* (either as a string or an array) and displays
* it using the specified template.
*
* @access private
* @param string the heading
* @param string the message
* @param string the template name
* @param int the status code
* @return string
*/
function show_error($heading, $message, $template = 'error_general', $status_code = 500)
{
set_status_header($status_code);

$message = '<p>'.implode('</p><p>', ( ! is_array($message)) ? array($message) : $message).'</p>';

if (ob_get_level() > $this->ob_level + 1)
{
ob_end_flush();
}

$module = CI::$APP->router->fetch_module();
$found = false;
foreach (Modules::$locations as $location => $offset) {
if (is_dir($source = $location.$module.'/errors/') && !$found && file_exists($location.$module.'/errors/'.$template.'.php')) {
$found = true;
ob_start();
include($source.$template.'.php');
$buffer = ob_get_contents();
ob_end_clean();
return $buffer;
break;
}
}
if (!$found)
{
ob_start();
include(APPPATH.'errors/'.$template.'.php');
$buffer = ob_get_contents();
ob_end_clean();
return $buffer;
}
}

// --------------------------------------------------------------------

/**
* Native PHP error handler
*
* @access private
* @param string the error severity
* @param string the error string
* @param string the error filepath
* @param string the error line number
* @return string
*/
function show_php_error($severity, $message, $filepath, $line)
{
$severity = ( ! isset($this->levels[$severity])) ? $severity : $this->levels[$severity];

$filepath = str_replace("\\", "/", $filepath);

// For safety reasons we do not show the full file path
if (FALSE !== strpos($filepath, '/'))
{
$x = explode('/', $filepath);
$filepath = $x[count($x)-2].'/'.end($x);
}

if (ob_get_level() > $this->ob_level + 1)
{
ob_end_flush();
}
ob_start();
include(APPPATH.'errors/error_php.php');
$buffer = ob_get_contents();
ob_end_clean();
echo $buffer;
}


}
// END Exceptions Class

/* End of file Exceptions.php */
/* Location: ./system/core/Exceptions.php */


I have an error on line 48
CI not define

Can u help me?