Exception: No suitable position found to insert

Hi! I'm encountering an exception using this component. I can reliably reproduce this in my application in a very specific situation but I haven't been able to produce a minimal example so I'm hoping a description helps narrowing this down. It also seems to depend on timing.

The exception is:
```
Error: No suitable position found to insert.
at insertNode (C:\Work\NMM2\node_modules\react-sortable-tree\dist\umd\webpack:\src\utils\tree-data-utils.js:801:15)
at memoizedInsertNode (C:\Work\NMM2\node_modules\react-sortable-tree\dist\umd\webpack:\src\utils\memoized-tree-data-utils.js:35:35)
at ReactSortableTree.value (C:\Work\NMM2\node_modules\react-sortable-tree\dist\umd\webpack:\src\react-sortable-tree.js:244:29)
at Object.hover (C:\Work\NMM2\node_modules\react-sortable-tree\dist\umd\webpack:\src\utils\drag-and-drop-utils.js:130:25)
at Target.hover (C:\Work\NMM2\node_modules\react-dnd\lib\createTargetFactory.js:71:14)
at DragDropManager.hover (C:\Work\NMM2\node_modules\dnd-core\lib\actions\dragDrop.js:139:13)
at Object.hover (C:\Work\NMM2\node_modules\dnd-core\lib\DragDropManager.js:92:38)
at HTML5Backend.handleTopDragOver (C:\Work\NMM2\node_modules\react-dnd-html5-backend\lib\HTML5Backend.js:539:20)
```

What I do is:
- Have a tree with two roots, the first has multiple children, the second only one.
- Expand the second root
- Quickly drag the second root element across its sole child and outside the tree div. The exception happens before I release the mouse button.

It may be noteworthy that by the time the exception happens the "canDrop" callback has never been invoked.