deal with 'non-admin area' warn

We usually use the follow code to delete product in Magento

$product = Mage::getSingleton('catalog/product')->load($productId);
$product->delete();

Of course, you are given a warn from magento. To solve this problem, you should add the follow code before and after delete

　　Mage::register('isSecureArea', true);

　　Mage::unregister('isSecureArea', true);