Fix: un produit d'une zone libre ne doit pas tre incrŽmentŽ lors du passage en mode brouillon d'une commande client lorsque la dŽcrŽmentation du stock se fait sur les commandes

Fix: If multiprice is enabled and level is not defined for customer, we always use the level 1. We can't use the denormalized price stored in product table as this price is the last price saved (it might be any level) and should never bee seen by user when multiprice is activated.
So we force the level to 1 if not defined.