Error: Cannot add to children defined by a function

Tried to keep the demo as simple as possible.
https://codesandbox.io/s/2oko3wl8v0

Scenario:
Try to drag a node under another node which has a lazy loader function as value children property.

Result:
It throws error stated below:
```
Cannot add to children defined by a function
addNodeAtDepthAndIndex
https://2oko3wl8v0.codesandbox.io/node_modules/react-sortable-tree/dist/main.js:553:63
addNodeAtDepthAndIndex/newChildren<
https://2oko3wl8v0.codesandbox.io/node_modules/react-sortable-tree/dist/main.js:621:33
addNodeAtDepthAndIndex
https://2oko3wl8v0.codesandbox.io/node_modules/react-sortable-tree/dist/main.js:619:64
addNodeAtDepthAndIndex/newChildren<
https://2oko3wl8v0.codesandbox.io/node_modules/react-sortable-tree/dist/main.js:621:33
addNodeAtDepthAndIndex
https://2oko3wl8v0.codesandbox.io/node_modules/react-sortable-tree/dist/main.js:619:64
insertNode
https://2oko3wl8v0.codesandbox.io/node_modules/react-sortable-tree/dist/main.js:676:32
memoizedInsertNode
https://2oko3wl8v0.codesandbox.io/node_modules/react-sortable-tree/dist/main.js:1199:37
value
https://2oko3wl8v0.codesandbox.io/node_modules/react-sortable-tree/dist/main.js:1468:201
hover
https://2oko3wl8v0.codesandbox.io/node_modules/react-sortable-tree/dist/main.js:2652:81
hover
https://2oko3wl8v0.codesandbox.io/node_modules/react-dnd/lib/createTargetFactory.js:71:5
hover
https://2oko3wl8v0.codesandbox.io/node_modules/dnd-core/lib/actions/dragDrop.js:139:3
bindActionCreator/<
https://2oko3wl8v0.codesandbox.io/node_modules/dnd-core/lib/DragDropManager.js:92:19
handleTopDragOver
https://2oko3wl8v0.codesandbox.io/node_modules/react-dnd-html5-backend/lib/HTML5Backend.js:563:4
```

Expectation:
Its fine with me if I cannot drag under a node which has lazy loader function as children. As we can control the drop operation by passing **canDrop** as prop, I tried to see the output when the issue occurs. But it seems the error gets thrown before **canDrop** is called.

But is there any way to stop the dragging under that specific node?