make sure activeElement has focus method then activeElement.focus()

## In IE11, If activeElement is a svg element, call focus() method cause error.

Internet Explorer Version: 11.0.9600.18893IS

![zm0e170000011s0urBF52](https://user-images.githubusercontent.com/25051945/63252531-944bd900-c2a2-11e9-91b6-d8d9e41dbfbb.png)

## demo
```html
<body>
  <svg>
  <circle id="mycircle"  cx="400" cy="300" r="50" />
<svg>
</body>
```