我尝试在组件中使用isFetching和error。但是，当我尝试使用useSelector从状态中选择用户时，在标题中出现错误。以下是我的代码：

const [username, setUsername] = useState("");
  const [password, setPassword] = useState("");
  const dispatch = useDispatch();
  const [isFetching, error] = useSelector((state)=>state.user)

  const handleClick = (e) => {
    e.preventDefault();
    login(dispatch, { username, password });
  };

和错误消息：

TypeError: Object is not iterable (cannot read property Symbol(Symbol.iterator))
Login
C:/Users/xxx/Shop/E-commerce/src/pages/Login.jsx:74
  71 |  const [username, setUsername] = useState("");
  72 |  const [password, setPassword] = useState("");
  73 |  const dispatch = useDispatch();
> 74 |  const [isFetching, error] = useSelector((state)=>state.user)
     | ^  75 |  
  76 | 
  77 |  const handleClick = (e) => {