Call to a member function ... on a non-object

[eluser]soluicius[/eluser]
Hello,
I followed this tutorial( https://tutsplus.com/course/codeigniter-best-practices/ - 04-Using Third Party Libraries) but i'm stuck while securing the pages.
I think spark doesn't load ion_auth model
I get this error:

Code:

A PHP Error was encountered

Severity: Notice

Message: Undefined property: Welcome::$ion_auth

Filename: controllers/welcome.php

Line Number: 9

Fatal error: Call to a member function logged_in() on a non-object in C:\wamp\www\application\controllers\welcome.php on line

Here is my controller:
1) user.php

Code:

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

class User extends CI_Controller {

public function __construct()
{
  parent::__construct();
  
}

public function login()
{
  echo 'Login form';
}

}

/* End of file user.php */
/* Location: ./application/controllers/user.php */

2) welcome.php

Code:

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

class Welcome extends CI_Controller {


public function __construct() {
  parent::__construct();

  if ($this->ion_auth->logged_in() == false) {
   redirect('user/login');
  }
}

/**
  * Index Page for this controller.
  *
  * Maps to the following URL
  *   http://example.com/index.php/welcome
  * - or -  
  *   http://example.com/index.php/welcome/index
  * - or -
  * Since this controller is set as the default controller in
  * config/routes.php, it's displayed at http://example.com/
  *
  * So any other public methods not prefixed with an underscore will
  * map to /index.php/welcome/<method_name>
  * @see http://codeigniter.com/user_guide/general/urls.html
  */
public function index()
{
  $this->load->view('welcome_message');
}
}

/* End of file welcome.php */
/* Location: ./application/controllers/welcome.php */

and in autoload.php i have:

Code:

$autoload['sparks'] = array('ion_auth');

Any suggestions?