the slot of unused view may be useless

Hi, thanks for your great job. I have a question about the unused view. If less items pass in RecycleScroller component, I should remove it using active.

```vue

```

My question is why not just remove the slot internal. I think unused view is useless for most users.

Original implements:

https://github.com/Akryum/vue-virtual-scroller/blob/8657880d6c8c52fd4abb04abc982a928d2fdf184/src/components/RecycleScroller.vue#L26-L40

I recommend remove it

```vue

```