The Form ref is none in render

[davycun]

• I have searched the issues of this repository and believe that this is not a duplicate.

Reproduction link

Steps to reproduce

1、click button
2、the Form input display none

What is expected?

first click the input display

What is actually happening?

input no show

Environment	Info
antd	4.0.3
React	16.13.0
System	mac os
Browser	chrome lastest

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//能不能在通过props初始化表单的时候就可以采用此form的引用
//否则通过编辑数据的时候，只能把关联字段必填与否通过state来实现，
//当Form字段关联比较多的时候就比较麻烦，需要搞很多state和onChange

[zombieJ]

与表单有关的操作都需要在 Form 的控制范围内。

https://codesandbox.io/s/antd-reproduction-template-l0bq9