The [bug report] selector does not display the bound value until the option is loaded, because option is often the one that requests the interface

### Element UI version
2.13.2

### OS/Browsers version
任何版本

### Vue version
3.0.0-beta.14

### Reproduction Link
https://jsfiddle.net/mmx38qxw/

### Steps to reproduce
选择器在option未加载前, 不要显示绑定的值,因为option经常是请求接口的,绑定的值一般是个id,但是option还没加载,他会先展示id,不应该这样,或者弄个属性设置

### What is Expected?
绑定的值一般是个id,但是option还没加载,他会先展示id,不应该这样

### What is actually happening?
他会展示id