Hello everybody, I have a problem with my module in Odoo 9 when I try to create a record in a one2many field, when I press the "Save" button I get the following error:

Traceback (most recent call last):
  File "/opt/odoo/openerp/http.py", line 648, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/opt/odoo/openerp/http.py", line 685, in dispatch
    result = self._call_function(**self.params)
  File "/opt/odoo/openerp/http.py", line 321, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/opt/odoo/openerp/service/model.py", line 118, in wrapper
    return f(dbname, *args, **kwargs)
  File "/opt/odoo/openerp/http.py", line 314, in checked_call
    result = self.endpoint(*a, **kw)
  File "/opt/odoo/openerp/http.py", line 964, in __call__
    return self.method(*args, **kw)
  File "/opt/odoo/openerp/http.py", line 514, in response_wrap
    response = f(*args, **kw)
  File "/opt/odoo/addons/web/controllers/main.py", line 892, in call_kw
    return self._call_kw(model, method, args, kwargs)
  File "/opt/odoo/addons/web/controllers/main.py", line 884, in _call_kw
    return getattr(request.registry.get(model), method)(request.cr, request.uid, *args, **kwargs)
  File "/opt/odoo/openerp/api.py", line 250, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/openerp/api.py", line 381, in old_api
    result = method(recs, *args, **kwargs)
  File "/opt/odoo/addons/mail/models/mail_thread.py", line 281, in write
    result = super(MailThread, self).write(values)
  File "/opt/odoo/openerp/api.py", line 248, in wrapper
    return new_api(self, *args, **kwargs)
  File "/opt/odoo/openerp/models.py", line 3846, in write
    self._write(old_vals)
  File "/opt/odoo/openerp/api.py", line 248, in wrapper
    return new_api(self, *args, **kwargs)
  File "/opt/odoo/openerp/api.py", line 574, in new_api
    result = method(self._model, cr, uid, self.ids, *args, **old_kwargs)
  File "/opt/odoo/openerp/models.py", line 4004, in _write
    result += self._columns[field].set(cr, self, id, field, vals[field], user, context=rel_context) or []
  File "/opt/odoo/openerp/osv/fields.py", line 829, in set
    obj.write(cr, user, [act[1]], act[2], context=context)
  File "/opt/odoo/openerp/api.py", line 250, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/openerp/api.py", line 381, in old_api
    result = method(recs, *args, **kwargs)
  File "/opt/odoo/addons/hr_vacas_new/hr_vacas_new.py", line 608, in write
    return super(Hrvacasnew_fechas, self).write(vals)
  File "/opt/odoo/openerp/api.py", line 248, in wrapper
    return new_api(self, *args, **kwargs)
  File "/opt/odoo/addons/mail/models/mail_thread.py", line 281, in write
    result = super(MailThread, self).write(values)
  File "/opt/odoo/openerp/api.py", line 248, in wrapper
    return new_api(self, *args, **kwargs)
  File "/opt/odoo/openerp/models.py", line 3846, in write
    self._write(old_vals)
  File "/opt/odoo/openerp/api.py", line 248, in wrapper
    return new_api(self, *args, **kwargs)
  File "/opt/odoo/openerp/api.py", line 574, in new_api
    result = method(self._model, cr, uid, self.ids, *args, **old_kwargs)
  File "/opt/odoo/openerp/models.py", line 4004, in _write
    result += self._columns[field].set(cr, self, id, field, vals[field], user, context=rel_context) or []
  File "/opt/odoo/openerp/osv/fields.py", line 856, in set
    if inverse_field.ondelete == "cascade":
  File "/opt/odoo/openerp/fields.py", line 360, in __getattr__
    raise AttributeError(name)
AttributeError: ondelete

Anyone could help me with this error?

Thank You so much!