fix: fix can't get correct state

[luhc228]

问题描述

当 model 中的 state 初始值为0时，通过 useModelState API 获取 state 报错。

原因为

 const selector = store.useSelector(state => state[name]);
        if (selector) { // 当这里的selector === 0 statement为faslse, 无法正常返回 modelstate
          return selector;
        }

fix

   if (selector !== undefined) { 
          return selector;
   }