That's the aim in this commit; to blow up if there isn't one. It means that the code is out of synch across components - likely because processing has a new publisher but there hasn't been a front-end deploy. 

Previously, things would blow up later on in the `OutputContentMerger` where it's, rightly, assumed a publisher is present. Was particularly gnarly to track down. Failing fast, on transformation from the db, would've made hunting this down a 30 second task, as opposed to 30 minutes.