If per-route body parser is an empty object we need to prevent defaults from running on that route

[dlongley]

From a quick read of the code, it looks like if per-route body parser options of {} is used, no body parser will be added for the route, however, the mechanism that is used to perform route-specific body parsing requires an entry on the route. We should add a test here and ensure this works as intended, and if not, add no-op entry for the route (or similar) to fix it in a bug fix release.

We might also want to support options of false or null for this use case.