[bug report] use keep alive in Vue, and return to the parent page after switching pages. The table height of element UI becomes smaller

### Element UI version
2.13.0

### OS/Browsers version
windows/Chrome 79.0.3945.88（正式版本） （64 位）

### Vue version
2.5.20

### Reproduction Link
https://jsfiddle.net/mmx38qxw/

### Steps to reproduce
主页面：
`

`

子页面：
`



{{ scope.row.date }}

姓名: {{ scope.row.name }}

住址: {{ scope.row.address }}

编辑
删除


`

### What is Expected?
期望table高度保持不变

### What is actually happening?
table高度变小