Issu form_validation

Help me to use xss_clean in form_validation?
i am trying still an error as below.
Unable to access an error message corresponding to your field name Username.
Unable to access an error message corresponding to your field name Password.

this my code to use xss_clean:

PHP Code:

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

class Login extends CI_Controller {
  function __construct(){
    parent::__construct();
    $this->load->helper(array('form','url'));
    // $this->load->model('m_login');
    $this->load->library(array('session', 'form_validation'));
  }
  function index()
  {
    $this->load->view('admin/v_login');
  }
  function valid(){
    $this->form_validation->set_error_delimiters('<div class="merah">', '</div>');
    $this->form_validation->set_rules('username', 'Username', 'required|xss_clean');
    $this->form_validation->set_rules('password', 'Password', 'required|xss_clean');
    if ($this->form_validation->run() == TRUE) {
      $data=array(
      'username'=>$this->input->post('username'),
      'password'=>$this->input->post('password') 
      );
      if ($data['username'] == 'admin' && $data['password'] == '1234') {
        $this->session->set_userdata($data);
        redirect('admin/login/sukses');
      }else{
        return TRUE;
      }

      
    }else{
      $this->load->view('admin/v_login');
    }
  }
  function sukses()
  {
    redirect('admin/dasabor', 'refresh');
  }
  function logout(){
    $this->session->sess_destroy();
    $this->load->view('admin/v_login');
  }
} 


and i set

PHP Code:

$config['global_xss_filtering'] = TRUE;