listMaxHeight does not work and no scroll in Fixed mode

The listMaxHeight does not work and no scroll in Fixed mode.
This problem also like : https://github.com/MoePlayer/APlayer/issues/277#issue-456161855

config:
```

const ap = new APlayer({
container: document.getElementById('aplayer'),
fixed: true,
autoplay: false,
theme: '#b7daff',
loop: 'all',
order: 'list',
preload: 'auto',
volume: 0.5,
lrcType: 3,
mutex: true,
listFolded: false,
listMaxHeight: 30,
```
pic:

I don't know if it doesn't work in this mode, or if my other styles affect it.

I use Aplayer in my blog using hexo-yilia,if I not update the blog,you can see the problem in my site <https://www.yansheng.xyz/>