A PHP Error was encountered

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
class Template{
    var $ci;
    function _construct(){
        $this->ci =& get_instance();

    }
    function load($loc,$tpl_name,$view,$data=null){

        if($loc=='admin' && $tpl_name=='default') {
            $tpl_name = 'admin';
        }
        if($loc=='public' && $tpl_name=='default'){
            $tpl_name='public';

        }

        $data['main']=$loc.'/'.$view;
        $this->ci->load->view('/templates/'.$tpl_name,$data);

    }
}


================
Message: Trying to get property of non-object
Filename: libraries/Template.php
Line Number: 19

=============
<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class dashboard extends CI_Controller {


    public function index()
    {
        
       $this->template->load('admin','default','dashboard');
    }
}


=================
Line: 10

Function: load 
==========
Can you help me to solve this problem ?