Interacting with an invisible node should fail

[icmdaf]

It's currently possible to interact with a node that is not visible, i.e. the interaction only succeeds in the test because the event is dispatched directly, but if the test emulated a system mouse and let the browser figure out the event it would have failed.

So it would be useful to have a check if getClientBoundingRect() is all-zero and return, as it's implemented already for pointer-events: none.