Missing or invalid Content-Type headers do not generate correct HTTP error codes

For POST requests with a missing Content-Type header, or an invalid one like "Content-Type: foo" or one with no deserialiser found like "Content-Type: foo/bar" the error generated is a 400 instead of 415.

I've managed to patch resteasy to fix the last first and third, but not the second case as the exception happes in the HttpServletDispatcher, as opposed to the SynchronousDispatcher where all error handling is done.