sort

Describe the bug

When using the Swap plugin, it's impossible to cancel a swap once the swap threshold has been met for an item. You can't drag the item back to its original place to prevent a swap. This happens with or without the revertOnSpill: true option.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://sortablejs.github.io/Sortable/#swap
2. Drag "Item 1" to h

The sorting does not seem to be working when the items are in a fixed height container that scroll all the items.

See this fiddle:
https://jsfiddle.net/ns5jg8L9/

If you try to drag the last item in the list to the top it won't scroll automatically and even if you use the mouse wheel to scroll while dragging it, dropping it on the top won't trigger a drop.

I guess this has something to do

I haven't gotten around to a few sections, would be awesome if we could at least have some friendly placeholders.