check if table has data

I would to conditionally launch an active start inverterter-node, in case a prior node doesnt’t have any data. By any data I don’t mean that it is empty and has 0 rows, but it not exist at all, for instance because the source file couldn’t be red and if I right click on the data outport, I see the flow variables only.

How to build a condition that tells whether this situation happened?

Thank you