Sergey

It seems works perfectly normal with empty lists already.  Raising an error just makes the work more inconvenient. It's normal situation when some objects are empty lists and nodes...

The principles are next - any object can be an empty list, empty ojects should not prevent a node from handling nonempty objects. And I guess if an input is...

The old version supported empty lists in the mask input too.  And I'm not sure about `None` values. As far as I know none of the nodes returns None....

Empty lists are not something wrong. They should not break nodes work. I'm, actually, quite satisfied with how the node currently works without the proposed changes.

 This is how you currently can handle your problem. I don't see the point of injecting None values since they break the work of next nodes.

One level lists are not supported even by List Mask Join node.  Nor rising an error nor inserting arbitrary values are not good solutions enough. If a node does...

Such solution is better because it does not break next nodes. But, at least in some cases, it can mix things up.  In the example there is an object...

In this case the node have to get two new inputs I guess - default values for True and default values for False. I think this is not so frequent...

I'm judging on number of reports about problems with empty objects. You probably can create an issue to describe your problem so it would be clear what is the motivation...

I guess that non perpendicular normal to the line AB is invalid input. The solution could be to project an invalid normal to perpendicular surface.