Magento Wishlist - Remove item

I've built a custom script to add and remove items to the wishlist using AJAX. Adding products is not a problem but I can't figure out how to remove an item. The Magento version is 1.5.1.0.

The script is in /scripts/ and looks like this:

include_once '../app/Mage.php';
 
 Mage::app();
 
 try{
     $type = (!isset($_GET['type']))? 'add': $_GET['type'];
     $id = (!isset($_GET['id']))? '': $_GET['id'];
 
     $session = Mage::getSingleton('core/session', array('name'=>'frontend'));
     $_customer = Mage::getSingleton('customer/session')->getCustomer();
 
     if ($type != 'remove') $product = Mage::getModel('catalog/product')->load($id);
 
     $wishlist = Mage::helper('wishlist')->getWishlist();
 
     if ($id == '')
         exit;
 
     if ($type == 'add')
         $wishlist->addNewItem($product);
     elseif ($type == 'remove')
         $wishlist->updateItem($id,null,array('qty' => 0));
 
     $products = Mage::helper('wishlist')->getItemCount();
     if ($type == 'add') $products++;
     if ($type == 'remove') $products--;
 
     $result = array(
         'result' => 'success',
         'type' => $type,
         'products' => $products,
         'id' => $id
     );
 
     echo json_encode($result);
 } 
 catch (Exception $e) 
 {
     $result = array( 
     'result' => 'error',
         'message' => $e->getMessage()
     );
     echo json_encode($result);
 }
 

So when I request the script with "remove" as $type and the wishlist item id as $id I get the following error:

Fatal error: Call to a member function getData() on a non-object in /[magento path]/app/code/core/Mage/Catalog/Helper/Product.php on line 389
 

When I look at the function updateItem() in /app/code/core/Mage/Wishlist/Model/Wishlist.php it expects a "buyRequest", but I can't figure out what that is.

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