Prestashop: How to allow deleting orders

AdminOrders.php

<?php

# version 1.4.8.2
# in file <folder-with-preshashop>/admin/tabs/AdminOrders.php
# find line "$this->colorOnBackground = true;", after that write: $this->delete = true;

#...
class AdminOrders extends AdminTab
{
	public function __construct()
	{
		global $cookie;

	 	$this->table = 'order';
	 	$this->className = 'Order';
	 	$this->view = true;
		$this->colorOnBackground = true;
		$this->delete = true;

#...