Thought inducing, as ever, but I don't like it :-). I would say that a null catalog is an invalid state for the Controller (and would even have asserts). This trick is effectively using invalid state isn't it?
I very much like the smell leading to the identification of an opportunity to separate concerns, and I understand the pushback unfortunately. As programmers we tend to optimise for code size of all things!, but yes, in this example I would split them.