I want to use pagination in CI but when i click on links i get the error invalid argument supplied for for each. I get a category id from link by get method. The first link is working but when I click it again, it doesn't work. Here is my link:

topic_title ?>

i don't know why its not working. please guide me here is my controller

public function categories()
{
     $cat_id = $this->input->get('cate',TRUE);
     $data['cat_id'] = $cat_id;
     $data['categories_list'] = $this->mod_forum->categories_list();
     $count = $this->mod_forum->record_count_sort($data);

     $data['categories_pic'] = $this->mod_forum->categories_pic($data);


    $config = array();
    $config["base_url"] = base_url() . "index.php/forum/categories?cat=$cat_id";
    $config["total_rows"] = $count->num_rows();
    $config["per_page"] = 5;
    $config["uri_segment"] = 3;
    $config["cat_id"] = $cat_id;

    $this->pagination->initialize($config);

    $page = ($this->uri->segment(3)) ? $this->uri->segment(3) : 0;
    $data["topics_sort"] = $this->mod_forum->fetch_sort_category($config["per_page"], $page,$config["cat_id"]);

    $data["sort"] = $this->pagination->create_links();
    $this->load->view('header');
    $this->load->view('navi');
    $this->load->view('forum/category_content',$data);
    $this->load->view('footer');

}

this is my model

public function record_count_sort($data) {
    return $this->db->get_where('topics',array('cat_id'=>$data['cat_id']));
    }

    public function fetch_sort_category($limit, $start,$cat_id) {
        $this->db->limit($limit, $start);
        $query = $this->db->get_where('topics',array('cat_id'=>$cat_id));
        if ($query->num_rows() > 0) {
            foreach ($query->result() as $row) {
                $data[] = $row;
            }
            return $data;
        }
        return false;
   }

this is my view