The default value of the a-select component must be undefined to trigger the placeholder attribute display

[sdutwsl]

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

Version

2.1.4

Environment

Windows 10 ,Chrome 90.0, Vue 2

Reproduction link

Steps to reproduce

参考codesandbox的链接

What is expected?

当select的v-model为null或者空字符串的时候，也应当显示placeholder，或者单独一个属性控制placeholder是否显示

What is actually happening?

当且仅当v-model为undefined时，才会显示placeholder，众所周知，大家都不想在代码中出现undefined

[github-actions]

This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 7 days

[zkwolf]

ant-design/ant-design#2367

[WormGirl]

这特性也太奇怪了， 一点也不合适，超级难用， 希望重新审视， 版本3.1.0-rc.5 不管是null 还是undefind placeholder都不会显示

[github-actions]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.