fix: Fix the issue of useWatch name being undefined returning {}

[crazyair]

因为 lodash get({ data: 11 }, undefined) 返回的是 undefined，而不是 {}，所以 name 为 undefined 需要返回 undefined

[vercel]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.43%. Comparing base (45cc9fa) to head (08b52d8).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #690   +/-   ##
=======================================
  Coverage   99.43%   99.43%           
=======================================
  Files          18       18           
  Lines        1247     1249    +2     
  Branches      304      290   -14     
=======================================
+ Hits         1240     1242    +2     
  Misses          7        7           

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[zombieJ]

useWatch(undefined) 等价于 useWatch()，应该是返回全量才对，不应该是 undefined

[crazyair]

useWatch(undefined) 等价于 useWatch()，应该是返回全量才对，不应该是 undefined

全量返回是用 [] 来表示的，这个也是这个库的规范

[crazyair]

我写了个示例，你看看

const Demo = ({ name }: { name?: string }) => {
  const value = Form.useWatch(name);
  console.log('value', value);
  return <div />;
};

如果调用 Demo 组建没传 name，那 value 则是 {} ，如果用户想 value 是 undefined，需要这样调用 <Demo name='' />

name='' 传给 useWatch 后，是 ['']，用 rc-util 的 get 返回的就是 undefined。

[crazyair]

https://github.com/lodash/lodash/blob/main/src/.internal/baseGet.ts#L21 lodash 是 index 有值才返回 object，否则返回 undefined