We recently installed the lunch module on a completely new and clean database (so no custom stuff) to test out what we could do with it. Now, everything was going well untill we wanted to send out to orders via mail. Our incoming and outgoing mail server is correctly configured in Odoo, so this is definitely not the problem, I think it has something to do with mas mailing, but I'm not to sure. Here is the full traceback of the error we got:

Odoo Server Error
Traceback (most recent call last):   File "/usr/lib/python3/dist-packages/odoo/http.py", line 654, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 312, in _handle_exception
    raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
  File "/usr/lib/python3/dist-packages/odoo/tools/pycompat.py", line 87, in reraise
    raise value
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 696, in dispatch
    result = self._call_function(**self.params)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 344, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/odoo/service/model.py", line 97, in wrapper
    return f(dbname, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 337, in checked_call
    result = self.endpoint(*a, **kw)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 939, in __call__
    return self.method(*args, **kw)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 517, in response_wrap
    response = f(*args, **kw)
  File "/usr/lib/python3/dist-packages/odoo/addons/web/controllers/main.py", line 966, in call_button
    action = self._call_kw(model, method, args, {})
  File "/usr/lib/python3/dist-packages/odoo/addons/web/controllers/main.py", line 954, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/usr/lib/python3/dist-packages/odoo/api.py", line 749, in call_kw
    return _call_kw_multi(method, model, args, kwargs)
  File "/usr/lib/python3/dist-packages/odoo/api.py", line 736, in _call_kw_multi
    result = method(recs, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/odoo/addons/mail/wizard/mail_compose_message.py", line 193, in action_send_mail
    self.send_mail()
  File "/usr/lib/python3/dist-packages/odoo/addons/mail/wizard/mail_compose_message.py", line 252, in send_mail
    all_mail_values = wizard.get_mail_values(res_ids)
  File "/usr/lib/python3/dist-packages/odoo/addons/mail/wizard/mail_compose_message.py", line 287, in get_mail_values
    records = self.env[self.model].browse(res_ids)
  File "/usr/lib/python3/dist-packages/odoo/api.py", line 821, in __getitem__
    return self.registry[model_name]._browse((), self)
  File "/usr/lib/python3/dist-packages/odoo/modules/registry.py", line 176, in __getitem__
    return self.models[model_name]
KeyError: False

Any help is very much appreciated.

Kind regards.