[bug] slider breaks on SSR when vertical is true

### Issue Reproduction
https://codesandbox.io/s/9wrmql2xo
(or see [live site](https://9wrmql2xo.sse.codesandbox.io/))

### Description
- slider **breaks** on SSR + `vertical: true`.
- SSR works **as expecte**d when `vertical: false`

## React SSR render (using next.js)

## React Browser render

## slick settings
```
{
dots: true,
infinite: false,
vertical: true,
verticalSwiping: true,
slidesToShow: 3,
slidesToScroll: 1
}
```