do not suppress product in the "basket" when quantity is zero
today, when a quantity of a product becomes zero, it is immediately removed from the basket, this could sound as a good behavior, but actually is not very ergonomic :
- when returning a product, one makes a long click on the product and then click return making it appear with "-1" quantity. in order to make a "-2", it is actually needed to press once on "-". if by mistake one pushes "+" then the product quantity becomes zero and the line disapear.... Grrr
- that would allow also to return a product with the barcode : one scan create the product in the basket with "+1", and then 2 pression on "-" would make it appear with "-1".
then the "garbage" icon is still there to remove the line completely.