Message: Call to a member function helper() on null

Filename: D:wampwwwcodeigniterapplicationhooksLanguageLoader.php

class LanguageLoader
{
    function initialize() {
        $ci =& get_instance();
        $ci->load->helper('language');

        $site_lang = $ci->session->userdata('site_lang');
        if ($site_lang) {
            $ci->lang->load('message',$ci->session->userdata('site_lang'));
        } else {
            $ci->lang->load('message',$ci->session->userdata('site_lang'));
        }
    }
}

class LanguageLoader
{
    function initialize() {
        $CI =& get_instance();
        if ($CI === null) {
            new CI_Controller();
            $CI =& get_instance();
        }
        $CI->load->helper('language');

        $site_lang = $CI->session->userdata('site_lang');
        if ($site_lang) {
            $CI->lang->load('message',$CI->session->userdata('site_lang'));
        } else {
            $CI->lang->load('message',$CI->session->userdata('site_lang'));
        }
    }
}

Message: call_user_func_array() expects parameter 1 to be a valid callback, class 'Error' does not have a method 'my404'

Filename: core/CodeIgniter.php

call_user_func_array(array(&$CI, $method), $params);

class Error extends My_Controller {
    public function my404() {
        //Code to show my 404 template
    }
}