Submit cannot be triggered twice after upload manually

### Element UI version
2.10.0

### OS/Browsers version
chrome 79.0.3945.117

### Vue version
2.5.17

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

### Steps to reproduce
upload 手动上传之后无法二次触发submit

### What is Expected?
希望可以直接再次提交

### What is actually happening?
upload 手动上传之后, 接口返回失败，此时再次点击上传无法二次触发submit。除非手动移除文件再上传