Error al finalizar tarea / SRV externo

RPC_ERROR
Odoo Server Error
Traceback (most recent call last):
  File "/home/odoo/src/odoo/odoo/addons/base/models/ir_http.py", line 242, in _dispatch
    result = request.dispatch()
  File "/home/odoo/src/odoo/odoo/http.py", line 702, in dispatch
    result = self._call_function(**self.params)
  File "/home/odoo/src/odoo/odoo/http.py", line 368, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/home/odoo/src/odoo/odoo/service/model.py", line 94, in wrapper
    return f(dbname, *args, **kwargs)
  File "/home/odoo/src/odoo/odoo/http.py", line 357, in checked_call
    result = self.endpoint(*a, **kw)
  File "/home/odoo/src/odoo/odoo/http.py", line 925, in __call__
    return self.method(*args, **kw)
  File "/home/odoo/src/odoo/odoo/http.py", line 546, in response_wrap
    response = f(*args, **kw)
  File "/home/odoo/src/odoo/addons/web/controllers/main.py", line 1328, in call_button
    action = self._call_kw(model, method, args, kwargs)
  File "/home/odoo/src/odoo/addons/web/controllers/main.py", line 1316, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/home/odoo/src/odoo/odoo/api.py", line 471, in call_kw
    result = _call_kw_multi(method, model, args, kwargs)
  File "/home/odoo/src/odoo/odoo/api.py", line 456, in _call_kw_multi
    result = method(recs, *args, **kwargs)
  File "/home/odoo/src/user/odoo-mastercore/isp_addons/helpdesk_subscription_isp/wizard/helpdesk_ticket_create_timesheet.py", line 21, in save_timesheet
    self.task_id.action_fsm_validate()
  File "/home/odoo/src/user/odoo-mastercore/isp_addons/helpdesk_subscription_isp/models/project_task.py", line 120, in action_fsm_validate
    [user.partner_id.mobile], _( "El Ticket %s fue resuelto!", self.helpdesk_ticket_id.name)
Exception

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/odoo/src/odoo/odoo/http.py", line 658, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/home/odoo/src/odoo/odoo/http.py", line 301, in _handle_exception
    raise exception.with_traceback(None) from new_cause
AttributeError: 'res.partner' object has no attribute 'partner_id'