An HTTP server may return the response code 204 in a scenario where a request was enacted but the response does not include any entity content. See https://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.7

In this scenario the common REST client wrongly tries to read an entity from the client response, leading to an exception being thrown. The caller of the REST client will then be presented with a response code of 500 (Internal Server Error).