codeigniter_model_controller_error

//problem: can't load model in the controller constructor

//url
http://codeigniter/index.php/news/create/

//routing

$route['news/create'] = 'news/create';

//controller

<?php
class News extends CI_Controller {

    function __construct()
    {
        parent::__construct();
        $this->load->model('news_model');
    }

    public function index(){
        $data['news'] = $this->news_model->get_news();
        $data['title'] = 'News archive';

        $this->load->view('templates/header', $data);
        $this->load->view('news/index', $data);
        $this->load->view('templates/footer', $data);
    }

    public function view($slug){
        $data['news_item'] = $this->news_model->get_news('$slug');
        if (empty($data['news_item'])) {
            show_404();
        }

        $data['title'] = $data['news_item']['title'];

        $this->load->view('templates/header', $data);
        $this->load->view('news/view', $data);
        $this->load->view('templates/footer', $data);

    }

    public function create(){
        $this->load->helper('form');
        $this->load->library('form_validation');
        $data['title'] = 'Create a news item';
        $this->form_validation->set_rules('title', 'Title', 'required');
        $this->form_validation->set_rules('text', 'text', 'required');

        if ($this->form_validation->run() === FALSE){
            $this->load->view('templates/header', $data);
            $this->load->view('news/create');
            $this->load->view('templates/footer');
        }else{
            $this->news_model->set_news();
            $this->load->view('news/success');
        }
    }
}

?>

//model
<?php

class News_model extends CI_Model
{

    function __construct()
    {
        parent::__construct();
        $this->load->database();
    }
}

public function get_news($slug === FALSE){
    if ($slug === FALSE) {
        $query = $this->db->get('news');
        return $query->result_array();
    }
    $query = $this->db->get_where('news', array('slug' => $slug));
    return $query->row_array();
}

public function set_news(){
    $this->load->helper('url');
    $slug = url_title($this->input->post('title'), 'dash', TRUE);

    $data = array(
        'title' => $this->input->post('title'),
        'slug' => $slug,
        'text' => $this->input->post('text')
         );
    return $this->db->insert('news', $data);
}


?>