Url to cart page includes the path to top level catalog page

[borro]

Hello. I'm testing VM 3.0.9 at Joomla 3.4.1.

I added the menu item of Vm Category type to the my unpublished menu on site. I selected the top level category for this menu item to see all categories. The alias for this menu item is "catalog". I had this link at the previous site version in published menu but now I don'need it but i don't want browser to show 404 error or make some redirection.
After that the url to cart page had become look like site/catalog/cart. If there is no "catalog" menu item the url to cart look like site/component/virtuemart/cart?Itemid=0. I want the url to cart to be looks like site/cart
What did I do wrong? Or is it a bug?