Do not remove 'Content-Length' header even for a message with empty content - HEAD requires that

src/main/java/org/jboss/netty/handler/codec/http/HttpMessageDecoder.java

@@ -210,7 +210,6 @@ public abstract class HttpMessageDecoder extends ReplayingDecoder<HttpMessageDec
                 // No content is expected.
                 // Remove the headers which are not supposed to be present not
                 // to confuse subsequent handlers.
-                message.removeHeader(HttpHeaders.Names.CONTENT_LENGTH);
                 message.removeHeader(HttpHeaders.Names.TRANSFER_ENCODING);
                 return message;
             } else {