canNodeHaveChildren not called if there is no row above.

As far as I can gather, there is no way to prevent showing the hover preview if hovering over the first level of the tree, because canNodeHaveChildren is not called.

I can see in the source code:

````
if (rowAbove) {
var path = rowAbove.path;
var aboveNodeCannotHaveChildren = !this.treeRef.canNodeHaveChildren(rowAbove.node);

if (aboveNodeCannotHaveChildren) {
path = path.slice(0, path.length - 1);
} // Limit the length of the path to the deepest possible

dropTargetDepth = Math.min(path.length, dropTargetProps.path.length);
}
````
Where canNodeHaveChildren is only called if there is a row above.

So, my question is: is there a way to prevent the hover preview for the first level of the tree?

Thanks!