ctn-waterloo/nengo — pull request #287 by hunse (2014-03-18 18:27:25+00:00)
Title: Error if node `output` returns none (fixes #286)

@tcstewar : is this what you wanted? It might make things a bit slower, since it has to happen every time step, but only very slightly. I think the performance cost is worth it. Is checking for NaNs good as well? I can't see when we would ever want to return these.