Walter just shakes his head. "Nothing worth going over."

Alright, so it's not really nothing. It's a big something but he feels like a complete dipshit at the moment and would rather not explain all the ways in which he actually is one. That and, really, it shouldn't have bothered him as much as it did. Admitting what it was and that it did means admitting a whole hell of a lot of things that he can't even begin to deal with right now.