message: properly cast NULL list to varchar
diff: @@ -543,27 +543,22 @@ static bool BlobCastSwitch(Vector &source, Vector &result, idx_t count, string *
  static bool ValueStringCastSwitch(Vector &source, Vector &result, idx_t count, string *error_message) {
  switch (result.GetType().id()) {
  case LogicalTypeId::VARCHAR:
  - case LogicalTypeId::JSON: {
  - ValidityMask *result_validity;
  + case LogicalTypeId::JSON:
  if (source.GetVectorType() == VectorType::CONSTANT_VECTOR) {
  result.SetVectorType(source.GetVectorType());
  - result_validity = &ConstantVector::Validity(result);
  } else {
  result.SetVectorType(VectorType::FLAT_VECTOR);
  - result_validity = &FlatVector::Validity(result);
  }
  - VectorData source_data;
  - source.Orrify(count, source_data);
  for (idx_t i = 0; i < count; i++) {
  - if (!source_data.validity.RowIsValid(source_data.sel->get_index(i))) {
  - result_validity->SetInvalid(i);
  - }
  auto src_val = source.GetValue(i);
  + if (src_val.IsNull()) {
  + result.SetValue(i, Value(result.GetType()));
  + } else {
  auto str_val = src_val.ToString();
  result.SetValue(i, Value(str_val));
  }
  - return true;
  }
  + return true;
  default:
  return TryVectorNullCast(source, result, count, error_message);
  }
  