[bug] Removing an element while it is dragged throws an error

[wdoug]

Reproduction

Scenario

https://codesandbox.io/s/still-wildflower-qugs0?file=/src/index.js

Steps to Reproduce

Summary of steps if applicable.

1. Drag any of the elements on the page
2. Wait for that element to be removed
3. See error thrown

Describe the bug

An error is thrown. This in turn can create cascading issues where elements aren't removed or updated properly or break other libraries that use this one (example from react-sortablejs).

Expected behavior

Version

package	version
sortablejs	^1.12.0
@types/sortablejs	N/A

Additional Context

I would expect when an element that you are dragging is removed it would immediately be removed from the DOM the drag would be canceled. This is what happens with jquery-ui's Sortable implementation (which happens to be the legacy UI that we are trying to replace with Sortablejs). I don't know if jQuery-UI supports HTML5 drag and drop though, so I'm not sure how useful referencing their implementation is.