rn的List 中存在多余的边框

[zim-lee]

Version

2.1.1

Environment

rn 0.50.3, antd-mobile 2.1.1

Reproduction link

http://oxr3qa4p3.bkt.clouddn.com/TIM-20171215123600.png

Steps to reproduce

Item对应的thumb中放置足够大的图片，就会出现多余的边框，如截图:

What is expected?

没有边框

What is actually happening?

有边框

[ant-design-bot]

It will be better to write your issue/comment in English, so more people can understand you.
And this means that more people can help you or benefit from your issue/comment.
See: ant-design/ant-design#4897

[warmhug]

自己覆盖样式吧，ref #1853 6ab912f