[FIX] account_facturx: fixed traceback

issue: a traceback is faced when configured a journal alias to create
invoice/bill when fetching emails with a pdf file from that alias.

closes odoo/odoo#34740

Task: 34740
Closes: #34740
Signed-off-by: oco-odoo <oco-odoo@users.noreply.github.com>

addons/account_facturx/models/account_move.py

@@ -222,15 +222,7 @@ class AccountMove(models.Model):
         res = super(AccountMove, self).message_post(**kwargs)
 
         if 'no_new_invoice' not in self.env.context and len(self) == 1 and self.state == 'draft':
-            # Get attachments.
-            # - 'attachments' is a namedtuple defined in mail.thread looking like:
-            # _Attachment = namedtuple('Attachment', ('fname', 'content', 'info'))
-            # - 'attachment_ids' is a list of ir.attachment records ids.
-            attachments = kwargs.get('attachments', [])
-            if kwargs.get('attachment_ids'):
-                attachments += self.env['ir.attachment'].browse(kwargs['attachment_ids'])
-
-            for attachment in attachments:
+            for attachment in res.attachment_ids:
                 self._create_invoice_from_attachment(attachment)
         return res