message: Special-case NULL values
diff: @@ -111,8 +111,12 @@ Value RApiTypes::SexpToValue(SEXP valsexp, R_len_t idx) {
  }
  case RType::TIMESTAMP: {
  auto ts_val = NUMERIC_POINTER(valsexp)[idx];
  + bool is_null = RTimestampType::IsNull(ts_val);
  + if (!is_null) {
  val = Value::TIMESTAMP(RTimestampType::Convert(ts_val));
  - val.is_null = RTimestampType::IsNull(ts_val);
  + } else {
  + val = Value(LogicalType::TIMESTAMP);
  + }
  break;
  }
  case RType::DATE: {
  