Weird behavior with nested SplitPanes

[pcdv]

Describe the bug

When I have two nested SplitPanes, the deepest one can be dragged above (or under) its parent.

Not sure if it is a bug or I'm doing something wrong. Maybe it's just a matter of adding the right CSS somewhere.

But it looks like the split can be moved outside of its expected min/max size. The
behavior is the same when changing split from horizontal to vertical.

To Reproduce

See https://codesandbox.io/s/fancy-thunder-n68cg

Expected behavior

It should not be possible to drag the split outside the bounds of its container.

Screenshots

Additional context

I'm using react-split-pane in https://github.com/pcdv/react-docky

[pcdv]

Found out that the behavior is a bit better if I set primary="second". At least, the first split cannot make the blue div disappear. But the green div can still be dragged over the two other ones.