mass_editing: TypeError: 'NoneType' object is not callable

gistfile1.txt

Traceback (most recent call last):
  File "/opt/odoo/odoo-server/openerp/http.py", line 530, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/opt/odoo/odoo-server/openerp/http.py", line 567, in dispatch
    result = self._call_function(**self.params)
  File "/opt/odoo/odoo-server/openerp/http.py", line 303, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/opt/odoo/odoo-server/openerp/service/model.py", line 113, in wrapper
    return f(dbname, *args, **kwargs)
  File "/opt/odoo/odoo-server/openerp/http.py", line 300, in checked_call
    return self.endpoint(*a, **kw)
  File "/opt/odoo/odoo-server/openerp/http.py", line 796, in __call__
    return self.method(*args, **kw)
  File "/opt/odoo/odoo-server/openerp/http.py", line 396, in response_wrap
    response = f(*args, **kw)
  File "/opt/odoo/odoo-server/addons/web/controllers/main.py", line 936, in call_kw
    return self._call_kw(model, method, args, kwargs)
  File "/opt/odoo/odoo-server/addons/web/controllers/main.py", line 928, in _call_kw
    return getattr(request.registry.get(model), method)(request.cr, request.uid, *args, **kwargs)
  File "/opt/odoo/odoo-server/openerp/api.py", line 241, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/addons/calendar/calendar.py", line 649, in read
    data = super(ir_model, self).read(cr, uid, new_ids, fields=fields, context=context, load=load)
  File "/opt/odoo/odoo-server/openerp/api.py", line 241, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/openerp/models.py", line 3125, in read
    result = BaseModel.read(records, fields, load=load)
  File "/opt/odoo/odoo-server/openerp/api.py", line 239, in wrapper
    return new_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/openerp/models.py", line 3160, in read
    self._read_from_database(stored, inherited)
  File "/opt/odoo/odoo-server/openerp/api.py", line 239, in wrapper
    return new_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/openerp/models.py", line 3338, in _read_from_database
    res2 = self._columns[f].get(cr, self._model, ids, f, user, context=context, values=result)
  File "/opt/odoo/odoo-server/openerp/osv/fields.py", line 770, in get
    records = comodel.search(domain, limit=self._limit)
  File "/opt/odoo/odoo-server/openerp/api.py", line 239, in wrapper
    return new_api(self, *args, **kwargs)
TypeError: 'NoneType' object is not callable

Hi Friend.
I have the same problem you to do a write in object "project.task" within a for