uc_cart_remove_item passes wrong item to hook

This is my first issue/bug report so any advice or feedback would be great!

The item passed to hook_cart_item() may not be the right item. This function re-pulls the items from the database. Upon doing so, it only matches on the node id and cart id. This leads to the wrong item possibly be passed along to the hook. It should also match on serialize($data). I've attached a patch that addresses this issue.