Element: [Bug, Report], el-tooltip, with, el-button, failed, to, popup, when,, using, Vue, 2.4.1

[zerob13]

Element UI version

1.3.7

OS/Browsers version

macOS 10.13| Ubuntu 16.04 LTS / Chrome 60.0.3122.66 beta

Vue version

2.4.1

Reproduction Link

https://jsfiddle.net/mksfL2sf/1/

Steps to reproduce

Follow code will failed with Vue 2.4.1 ,but works with 2.3.x
```

无效

If you add a div wrap ,the tooltips works again.
 ```
<el-tooltip class="item" effect="dark" content="Top Left 提示文字" placement="right">
  <div>
      <el-button>有效</el-button>
  </div>
  </el-tooltip>

What is Expected?

el-tooltips works with el-button

What is actually happening?

el-tooltips doesn't work with el-button

[Leopoldthecoder]

Fixed in #5916

[lazybonee]

Vue version 2.5.3
Element UI version 2.3.9
OS/Browsers version Windows 10/chrome 67.0.3396.79
El-tooltips don't work with el-button