message: Do not serialise if length of vector is 0
diff: @@ -41,8 +41,11 @@ namespace kv
  {
  const uint64_t size = entry.size();
  sb.write(reinterpret_cast<char const*>(&size), sizeof(size));
  + if (entry.size() > 0)
  + {
  sb.write(reinterpret_cast<char const*>(entry.data()), entry.size());
  }
  + }
  void clear()
  {
  