How to use try catch for unpivot?

I’m in situation where I extract columns for an unpivot operation through a regex selection on column names. The resulting column names configure value and remain columns for an unpivot node. It’s possible to have a situation where there are no value columns, which i need to mitigate. I’m trying to use the try/catch nodes to gracefully handle this, but so far I’ve not been successful. Do i misunderstand the way try-catch works?