[Bug Report] Table filter list oversizes when having lots of options

[AsukaShikinamiLangley]

Element UI version

2.3.9

OS/Browsers version

Chrome 66.0 x64

Vue version

2.5.17-beta.0

Reproduction Link

https://jsfiddle.net/coolucifer/r7o3tkxf/

Steps to reproduce

give table filter lots of values, press filter button

What is Expected?

it has a scroller

What is actually happening?

no scroller and oversizes