Filename中的错误：helign / url_helper.php在Codeigniter（CI）中

Question

我的代码是

function __construct() {
    parent::__construct();
    $this->load->library('session');
    $this->load->database();
    $this->load->model('Admin_model');
    $this->load->helper(array('form','file','url','security'));
}


public function update()
{

    if ($_POST){

        $this->config =  array(
              'upload_path'     => dirname($_SERVER["SCRIPT_FILENAME"])."/logo/",
              'upload_url'      => base_url()."logo/",
              'allowed_types'   => "gif|jpg|png|jpeg",
              'overwrite'       => TRUE,
              'max_size'        => "1000KB",
              'max_height'      => "768",
              'max_width'       => "1024"  
            );
        $this->load->library('upload', $this->config);
        if(!$this->upload->do_upload('logo'))
        {
             echo $this->upload->display_errors();
        }
        else
        {
            $finfo=$this->upload->data();

            $this->_createThumbnail($finfo['file_name']);

            $data['uploadInfo'] = $finfo;

            $data['thumbnail_name'] = $finfo['raw_name']. '_thumb' .$finfo['file_ext']; 

            print_r($finfo);
        }



}

}

public function _createThumbnail($filename)

{

    $config['image_library']    = "gd2";      

    $config['source_image']     = "logo/" .$filename;      

    $config['create_thumb']     = TRUE;      

    $config['maintain_ratio']   = TRUE;      

    $config['width'] = "80";      

    $config['height'] = "80";

    $this->load->library('image_lib',$config);

    if(!$this->image_lib->resize())

    {

        echo $this->image_lib->display_errors();

    }      

}

}

我已经加载了所有库，但它没有工作返回错误

A PHP Error was encountered

Severity: Notice

Message: Trying to get property of non-object

Filename: core/Loader.php

Line Number: 1213

Backtrace:

File: /var/www/html/relatio/application/admin/controllers/Admin.php
Line: 90
Function: library

File: /var/www/html/relatio/admin/index.php
Line: 293
Function: require_once


Fatal error: Call to a member function site_url() on a non-object in /var/www/html/relatio/system/helpers/url_helper.php on line 66
A PHP Error was encountered

Severity: Error

Message: Call to a member function site_url() on a non-object

Filename: helpers/url_helper.php

Line Number: 66

Backtrace:

接下来我该怎么办？建议请