[Bug Report] el-table if height is string type invalid in the new version

[happy0402]

Element UI version

2.9.1

OS/Browsers version

Chrome 版本 73.0.3683.86（正式版本）

Vue version

2.6.10

Reproduction Link

https://codepen.io/anon/pen/agpQjb

Steps to reproduce

没有步骤，你就看高度的样式就是错的

What is Expected?

style="height: 100%"

What is actually happening?

style="height: 100px"

[element-bot]

Translation of this issue:

Element UI version

2.9.1

OS/Browsers version

Chrome version 73.0.3683.86 (official version)

Vue version

2.6.10

Reproduction Link

Https://codepen.io/anon/pen/agpQjb

Steps to reproduce

Without steps, you would be wrong to look at the height pattern.

What is Expected?

Style= "height: 100%"

What is actually happening?

Style= "height: 100px"

[ziyoung]

#15858