Weird behaviour with onSelectNode

[sikula]

Describe the bug
onSelectNode appears to be called not only when a node is selected, but even clicking on the background (or any mouseUp action).

Expected behavior
onSelectNode only called when a node is clicked

Desktop (please complete the following information):

• OS: Linux
• Browser: Firefox

Additional context
This CodeSandbox has the same issue

[ajbogh]

This is expected behavior. When a node is selected the onSelectNode function will receive an INode object, when the background is clicked the argument will be null. When the argument is null the website's selectedNode state should be cleared, which will allow react-digraph to render the graph with no nodes selected.