Bullets Points Rendering Issue

## Wrong Bullets Points Rendering

Sometimes react-slick fails to generate the right number of bullets points

* See example here [CodeSandBox](https://codesandbox.io/s/50wl5n6wok)

Here react slicks should only render 2 bullets points, but there is 3, the last bullet point doesnt do anything

Reproduced with this config:
```
5 slides,
slidesToShow: 3,
slidesToScroll: 2
```