Yes, both your suggestions were my first thoughts too. The thing is A: no other node creation has a "cancel" option, the only reason this one could is because it depends on loading a file, but the cancel there is really for the file loading, not the node creation. So while it might make sense to people, it would not be "technically correct", B: I could see there being some possible reasons to have a Load-type node without actually specifying a file right-off, and certainly wouldn't want to make that impossible.
I think suppressing the error message is the best option, I just don't know how tricky that would be. It seems a simple thing, but it would basically be creating a special case for the error system, which is not always a good idea...
Something to ponder.
- Oshyan