upload在before upload时使用clearFiles方法报错

[q1998763]

http://element.eleme.io/#/zh-CN/component/upload

ElementUI version 1.2.5

OS/Browers version

Vue version

Reproduction Link

Steps to reproduce

Methods

需求是想只显示一个file item， 想法是在before upload 用 clearFiles 清除
demo:
http://jsfiddle.net/1qrkq5f1/

What is Expected?

What is actually happening?

[element-bot]

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