Smarty template engine: Unable to load template 'file:header.tpl' - php

Question

I developed a CodeIgniter application using Smarty template engine and Codeigniter 3.0.0, everything works well . But after upgrading Codeigniter (from 3.0.0 to 3.1.5) there is a Smarty error:
Unable to load template 'file:header.tpl'
Header.tpl is behind application/views/smarty_templates
I have a codeigniter library that recall Smarty Libraries:
<?php
require_once(APPPATH . 'third_party/smarty/libs/Smarty.class.php');
class CI_Smarty extends Smarty
{
function __construct()
{
parent::__construct();
$CI->load->config('smarty');
$this->ci = & get_instance();
log_message('debug',$this->setTemplateDir);
$this->compile_dir = "/tmp/.smarty_templates_c";
$this->template_dir = APPPATH . "views/smarty_templates";
$this->assign('APPPATH', APPPATH);
$this->assign('BASEPATH', BASEPATH);
$this->assign('SITEURL', site_url());
$this->assign('BASEURL', base_url());
// Assign CodeIgniter object by reference to CI
if (method_exists($this, 'assignByRef')) {
$ci =& get_instance();
$this->assignByRef("ci", $ci);
}
log_message('debug', "Smarty Class Initialized");
}
/**
* Parse a template using the Smarty engine
*
* This is a convenience method that combines assign() and
* display() into one step.
*
* Values to assign are passed in an associative array of
* name => value pairs.
*
* If the output is to be returned as a string to the caller
* instead of being output, pass true as the third parameter.
*
* #access public
* #param string
* #param array
* #param bool
* #return string
*/
function view($template, $data = array(), $return = FALSE)
{
foreach ($data as $key => $val) {
$this->assign($key, $val);
}
if ($return == FALSE) {
$CI =& get_instance();
if (method_exists($CI->output, 'set_output')) {
$CI->output->set_output($this->fetch($template));
} else {
$CI->output->final_output = $this->fetch($template);
}
return;
} else {
return $this->fetch($template);
}
}
}