错误:
Odoo Server Error

Traceback (most recent call last):
  File "/data/App/odoo12/odoo/models.py", line 4699, in ensure_one
    _id, = self._ids
ValueError: not enough values to unpack (expected 1, got 0)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/data/App/odoo12/odoo/http.py", line 654, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/data/App/odoo12/odoo/http.py", line 312, in _handle_exception
    raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
  File "/data/App/odoo12/odoo/tools/pycompat.py", line 87, in reraise
    raise value
  File "/data/App/odoo12/odoo/http.py", line 696, in dispatch
    result = self._call_function(**self.params)
  File "/data/App/odoo12/odoo/http.py", line 344, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/data/App/odoo12/odoo/service/model.py", line 97, in wrapper
    return f(dbname, *args, **kwargs)
  File "/data/App/odoo12/odoo/http.py", line 337, in checked_call
    result = self.endpoint(*a, **kw)
  File "/data/App/odoo12/odoo/http.py", line 939, in __call__
    return self.method(*args, **kw)
  File "/data/App/odoo12/odoo/http.py", line 517, in response_wrap
    response = f(*args, **kw)
  File "/data/App/odoo12/addons/web/controllers/main.py", line 966, in call_button
    action = self._call_kw(model, method, args, {})
  File "/data/App/odoo12/addons/web/controllers/main.py", line 954, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/data/App/odoo12/odoo/api.py", line 749, in call_kw
    return _call_kw_multi(method, model, args, kwargs)
  File "/data/App/odoo12/odoo/api.py", line 736, in _call_kw_multi
    result = method(recs, *args, **kwargs)
  File "/data/App/user-addons/std_oa/wizard/process_flow.py", line 40, in do_confirm
    return res.action_do_flow(operation, self.note)
  File "/data/App/user-addons/std_oa/models/models.py", line 778, in action_do_flow
    self._do_next()
  File "/data/App/user-addons/std_meeting_oa/models/models.py", line 163, in _do_next
    return super( StdOaMainInherit, self )._do_next ()
  File "/data/App/user-addons/std_oa/models/models.py", line 896, in _do_next
    return self.check_run_callback( 'done_flow' )
  File "/data/App/user-addons/std_oa/models/models.py", line 1239, in check_run_callback
    raise e
  File "/data/App/user-addons/std_oa/models/models.py", line 1234, in check_run_callback
    r = eval("model.%s()" % fn)
  File "<string>", line 1, in <module>
  File "/data/App/odoo12/addons/hr_holidays/models/hr_leave.py", line 657, in action_approve
    self.filtered(lambda hol: not hol.validation_type == 'both').action_validate()
  File "/data/App/odoo12/addons/hr_holidays/models/hr_leave.py", line 697, in action_validate
    employee_requests._validate_leave_request()
  File "/data/App/odoo12/addons/project_timesheet_holidays/models/hr_holidays.py", line 61, in _validate_leave_request
    fields.Datetime.from_string(holiday.date_to),
  File "/data/App/odoo12/addons/resource/models/resource_mixin.py", line 170, in list_work_time_per_day
    intervals = calendar._work_intervals(from_datetime, to_datetime, resource, domain)
  File "/data/App/odoo12/addons/resource/models/resource.py", line 265, in _work_intervals
    self._leave_intervals(start_dt, end_dt, resource, domain))
  File "/data/App/odoo12/addons/resource/models/resource.py", line 237, in _leave_intervals
    self.ensure_one()
  File "/data/App/odoo12/odoo/models.py", line 4702, in ensure_one
    raise ValueError("Expected singleton: %s" % self)
ValueError: Expected singleton: resource.calendar()