It depends on how you approach error propagation and handling in general in your application. There’s been some discussion about that - possible approaches include exceptions, Option, Either, Try, Validation, and further considerations will surface once (side) effects and/or async processing are involved. I don’t think there’s a clear-cut consensus regarding the “proper Scala way”, other than that using raw exceptions probably isn’t it.
As for null, in a Scala project I’d only expect this when interfacing with Java code - there I’d wrap it with Option#apply() and handle the None case as a failure. With StringUtils, I’d assume you’re validating user input, so Either or Validation might be appropriate.