[bug report] El cascade when emitpath is set to false. When the current selected content value is 0. Echo content is empty

[menglimu]

Element UI version

2.15.3

OS/Browsers version

win10 / Chrome 91

Vue version

2.6.14

Reproduction Link

https://codepen.io/menglimu/pen/QWvOLQR

Steps to reproduce

选择下拉中的第一个选项 '一致' 时，此时回显为空，选其他值正常

What is Expected?

回显出 label 一致

What is actually happening?

回显为空

[element-bot]

Translation of this issue:

Element UI version

2.15.3

OS/Browsers version

win10 / Chrome 91

Vue version

2.6.14

Reproduction Link

https://codepen.io/menglimu/pen/QWvOLQR

Steps to reproduce

When the first option "consistent" in the drop-down list is selected, the echo is blank at this time, and selecting other values is normal

What is Expected?

The label is consistent

What is actually happening?

Echo is empty