[FIX] account: fix ref when sending invoice to customer without email

Create a customer without email address, go on the accounting module
create an invoice for this customer.

Go back to the invoices list and select some of them including your
invoice for your customer without email address. Send them by mail.

You will have a traceback and the wizard will be broken.

This bug is caused by a change in the account module, there is no more
reference, they are replaced by the name of the invoice.

OPW-2085837

closes odoo/odoo#39738

Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>

addons/account/wizard/account_invoice_send.py

@@ -75,7 +75,7 @@ class AccountInvoiceSend(models.TransientModel):
                 if invoices:
                     wizard.invoice_without_email = "%s\n%s" % (
                         _("The following invoice(s) will not be sent by email, because the customers don't have email address."),
-                        "\n".join([i.reference for i in invoices])
+                        "\n".join([i.name for i in invoices])
                         )
                 else:
                     wizard.invoice_without_email = False