[16.0] sale_manual_delivery : AttributeError: '_unknown' object has no attribute 'id'

[dhp-denero]

Module

sale_manual_delivery

Describe the bug

RPC_ERROR Odoo Server Error : AttributeError: '_unknown' object has no attribute 'id'
On Sale Order --> Create Delivery button Clicked, instead of showing popup window, I am getting Odoo Server Error with bellow trace

Traceback (most recent call last):
  File "/home/odooagency/odoo16/odoo/odoo/http.py", line 1587, in _serve_db
    return service_model.retrying(self._serve_ir_http, self.env)
  File "/home/odooagency/odoo16/odoo/odoo/service/model.py", line 134, in retrying
    result = func()
  File "/home/odooagency/odoo16/odoo/odoo/http.py", line 1614, in _serve_ir_http
    response = self.dispatcher.dispatch(rule.endpoint, args)
  File "/home/odooagency/odoo16/odoo/odoo/http.py", line 1811, in dispatch
    result = self.request.registry['ir.http']._dispatch(endpoint)
  File "/home/odooagency/odoo16/odoo/addons/website/models/ir_http.py", line 235, in _dispatch
    response = super()._dispatch(endpoint)
  File "/home/odooagency/odoo16/odoo/odoo/addons/base/models/ir_http.py", line 154, in _dispatch
    result = endpoint(**request.params)
  File "/home/odooagency/odoo16/odoo/odoo/http.py", line 700, in route_wrapper
    result = endpoint(self, *args, **params_ok)
  File "/home/odooagency/odoo16/odoo/addons/web/controllers/dataset.py", line 42, in call_kw
    return self._call_kw(model, method, args, kwargs)
  File "/home/odooagency/odoo16/odoo/addons/web/controllers/dataset.py", line 33, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/home/odooagency/odoo16/odoo/odoo/api.py", line 461, in call_kw
    result = _call_kw_multi(method, model, args, kwargs)
  File "/home/odooagency/odoo16/odoo/odoo/api.py", line 448, in _call_kw_multi
    result = method(recs, *args, **kwargs)
  File "/home/odooagency/odoo16/odoo/odoo/models.py", line 6524, in onchange
    result['value'] = snapshot1.diff(snapshot0, force=first_call)
  File "/home/odooagency/odoo16/odoo/odoo/models.py", line 6343, in diff
    result[name] = field.convert_to_onchange(self[name], record, {})
  File "/home/odooagency/odoo16/odoo/odoo/fields.py", line 3005, in convert_to_onchange
    return super().convert_to_onchange(value._origin, record, names)
  File "/home/odooagency/odoo16/odoo/odoo/fields.py", line 970, in convert_to_onchange
    return self.convert_to_read(value, record)
  File "/home/odooagency/odoo16/odoo/odoo/fields.py", line 2981, in convert_to_read
    return value.id
AttributeError: '_unknown' object has no attribute 'id'

The above server error caused the following client error:
null

To Reproduce

Affected versions:
Version 16.0
Steps to reproduce the behavior:

1. Create Sale Quotation with Manual Delivery checkbox checked
2. Confirm Sales Order
3. Click On Create Delivery Button

Expected behavior
Expecting a Popup Window of Create Manual Delivery Action.

Additional context
I found that it is due to wrong model set on route_id field to manual.delivery.

    route_id = fields.Many2one(
        "stock.location.route",
        string="Use specific Route",
        domain=[("sale_selectable", "=", True)],
        ondelete="cascade",
        help="Leave it blank to use the same route that is in the sale line",
    )

This should be change to stock.route

    route_id = fields.Many2one(
        "stock.route",
        string="Use specific Route",
        domain=[("sale_selectable", "=", True)],
        ondelete="cascade",
        help="Leave it blank to use the same route that is in the sale line",
    )