Fix error when error on passing virtual order to 'Paid' status

If you create an order with a virtual product and pass it to 'Paid', if you didn't configure the store email, there was a blank page as the Tlog::debug method wasn't used correctly ( the second argument must be an array )

Moreover, you should be able to associate an online document to a product sale element, as it doesn't have anything to do with virtual products.