If a client sends application/ld+json as the content type, but no body, Fedora4 generates an uncaught exception. Yes this is a client error, but the server shouldn't give an internal server error as the response. Should probably be 400, as the request is just totally wrong.
$ curl -H "Content-Type: application/ld+json" -X PUT http://localhost:8080/rest/
org.apache.jena.atlas.AtlasException: com.fasterxml.jackson.core.JsonParseException: document doesn't start with a valid json element : null
at [Source: java.io.BufferedReader@57cec9d8; line: 1, column: 1]