[FIX] account: fix traceback when sending invoice without template

Create an invoice, click on send and print without an associated
template.

Traceback will occur because the lang parameter is set correctly only
from a template. Adding a fallback in case there is no template setting

opw-2168623

closes odoo/odoo#43008

X-original-commit: 8fd8fdcf0fa6fb26a1797ad2b40fcaf34d23eee2
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>

addons/account/models/account_move.py

@@ -2186,6 +2186,8 @@ class AccountMove(models.Model):
         lang = get_lang(self.env)
         if template and template.lang:
             lang = template._render_template(template.lang, 'account.move', self.id)
+        else:
+            lang = lang.code
         compose_form = self.env.ref('account.account_invoice_send_wizard_form', raise_if_not_found=False)
         ctx = dict(
             default_model='account.move',