message: Fix replication of set and insert of null values in lists
  Now the problem is fixed for all types - not just for Timestamp.
diff: @@ -473,26 +473,46 @@ void Lst<util::Optional<Double>>::set_repl(Replication* repl, size_t ndx, util::
  template <>
  void Lst<String>::set_repl(Replication* repl, size_t ndx, StringData value)
  {
  + if (value.is_null()) {
  + repl->list_set_null(*this, ndx);
  + }
  + else {
  repl->list_set_string(*this, ndx, value);
  }
  +}
  template <>
  void Lst<Binary>::set_repl(Replication* repl, size_t ndx, BinaryData value)
  {
  + if (value.is_null()) {
  + repl->list_set_null(*this, ndx);
  + }
  + else {
  repl->list_set_binary(*this, ndx, value);
  }
  +}
  template <>
  void Lst<Timestamp>::set_repl(Replication* repl, size_t ndx, Timestamp value)
  {
  + if (value.is_null()) {
  + repl->list_set_null(*this, ndx);
  + }
  + else {
  repl->list_set_timestamp(*this, ndx, value);
  }
  +}
  template <>
  void Lst<ObjKey>::set_repl(Replication* repl, size_t ndx, ObjKey key)
  {
  + if (key) {
  repl->list_set_link(*this, ndx, key);
  }
  + else {
  + repl->list_set_null(*this, ndx);
  + }
  +}
  /*************************** Lst<T>::insert_repl ****************************/
  template <>
  @@ -566,14 +586,24 @@ void Lst<util::Optional<Double>>::insert_repl(Replication* repl, size_t ndx, uti
  template <>
  void Lst<String>::insert_repl(Replication* repl, size_t ndx, StringData value)
  {
  + if (value.is_null()) {
  + repl->list_insert_null(*this, ndx);
  + }
  + else {
  repl->list_insert_string(*this, ndx, value);
  }
  +}
  template <>
  void Lst<Binary>::insert_repl(Replication* repl, size_t ndx, BinaryData value)
  {
  + if (value.is_null()) {
  + repl->list_insert_null(*this, ndx);
  + }
  + else {
  repl->list_insert_binary(*this, ndx, value);
  }
  +}
  template <>
  void Lst<Timestamp>::insert_repl(Replication* repl, size_t ndx, Timestamp value)
  @@ -589,8 +619,13 @@ void Lst<Timestamp>::insert_repl(Replication* repl, size_t ndx, Timestamp value)
  template <>
  void Lst<ObjKey>::insert_repl(Replication* repl, size_t ndx, ObjKey key)
  {
  + if (key) {
  repl->list_insert_link(*this, ndx, key);
  }
  + else {
  + repl->list_insert_null(*this, ndx);
  + }
  +}
  }
  #ifdef _WIN32
  