menuitem 在15以前可以有string=属性，但在15中去除了string=属性

Traceback (most recent call last):
  File "G:\od15\odoo\addons\base\models\ir_http.py", line 237, in _dispatch
    result = request.dispatch()
  File "G:\od15\odoo\http.py", line 694, in dispatch
    result = self._call_function(**self.params)
  File "G:\od15\odoo\http.py", line 365, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "G:\od15\odoo\service\model.py", line 94, in wrapper
    return f(dbname, *args, **kwargs)
  File "G:\od15\odoo\http.py", line 354, in checked_call
    result = self.endpoint(*a, **kw)
  File "G:\od15\odoo\http.py", line 923, in __call__
    return self.method(*args, **kw)
  File "G:\od15\odoo\http.py", line 541, in response_wrap
    response = f(*args, **kw)
  File "G:\od15\odoo\addons\web\controllers\main.py", line 1339, in call_button
    action = self._call_kw(model, method, args, kwargs)
  File "G:\od15\odoo\addons\web\controllers\main.