It would be very important to have an option in the shopping lists to automatically ignore products with a quantity of 0.

Currently, if you try to add a shopping list to the shopping cart that contains a product with a quantity of 0, you get an error message (The quantity (0) is incorrect.), see screenshot.

Of course you can simply remove the products from the shopping list, but this is a lot of extra work.

Example:

A merchant creates a shopping list for his groceries and orders them. After a week, the retailer walks through his warehouse and notices that some groceries are no longer in stock.

The merchant now has to remove every product from the shopping list that is still in stock in his warehouse, order the shopping list again and then manually add the products that have been removed previously.