How can we get the file path of the current document?

That sounds like the right call -- is the file unsaved? It might not have a file specification if its unsaved.

And as a tip: the error code can be decoded, though it doesn't always result in something useful. If you view it as hex and take each pair of digits (four pairs in all) and cast them to char, you'll spell out a four character code. It often indicates something more specific for an error than 'something went wrong'. If you look at the top of some headers, you'll see #defines for error codes like 'parm' or 't!nf'.