I added Packet.writeNull(). Also need to handle undefined value
   * In length calculation, do `if (val === null || typeof(val) == 'undefined') return ++length;` 
   * in serialisation loop - if (val === null) return packet.writeNull();  if (typeof val == 'undefined') return packet.writeInt8(0);` 

Also need to handle undefined (probably write empty string, not sure)