[Bug Report] autocomplete suggestion list round top-left corner only

[vera0119]

Element UI version

2.4.8

OS/Browsers version

chrome 69.0.3497.100

Vue version

2.5.2

Reproduction Link

Steps to reproduce

1. focus the autocomplete input
2. the suggestion list round top-left corner only

What is Expected?

autocomplete suggestion list round four corners

What is actually happening?

autocomplete suggestion list round top-left corner only

[ziyoung]

什么意思？不太理解。

[vera0119]

[vera0119]

箭头不见了 @liuchuzhang @ziyoung

[liuchuzhang]

很尴尬没有注意到这个:bowtie: