Return classes without ids fail silently

[baccatabob]

To reproduce:

1. Define MyClass without an Id field
2. Define MyClassResource correctly
3. Create a controller that returns List<MyClass>, with an ReturnsResource attribute pointing to MyClassResource

(I'm also doing authorisation using OAuth, and compression, but I don't think that these matter.)

The HTTP response will have a status of 200 but 0 length (and 0 contents).