msgpack-java-null-string

import org.msgpack.MessagePack;
import org.msgpack.annotation.MessagePackMessage;

public class Main {
    @MessagePackMessage
        public static class MyClass {
        public String str;
     }

    public static void main(String[] args) {
        MyClass src = new MyClass();
        src.str = null;

        // msgpack-java 4.1-devel throws NULL-pointer exception here.
        byte[] raw = MessagePack.pack(src);
    }
}