message: Issue Aggregate HashTable NullValue
  Replace hacky count extraction that relies on
  knowing the internals of the COUNT aggregate state
  with calls to finalize. As Codd intended.
diff: @@ -375,13 +375,13 @@ void GroupedAggregateHashTable::FetchAggregates(DataChunk &groups, DataChunk &re
  Vector addresses(LogicalType::POINTER);
  FindOrCreateGroups(groups, addresses);
  // now fetch the aggregates
  - idx_t col_offset = 0;
  for (idx_t aggr_idx = 0; aggr_idx < aggregates.size(); aggr_idx++) {
  D_ASSERT(result.ColumnCount() > aggr_idx);
  - auto &dest = result.data[aggr_idx];
  - VectorOperations::Gather::Set(addresses, dest, groups.size(), col_offset, aggr_idx);
  - col_offset += GetTypeIdSize(dest.GetType().InternalType());
  + auto &target = result.data[aggr_idx];
  + auto &aggr = aggregates[aggr_idx];
  + aggr.function.finalize(addresses, aggr.bind_data, target, result.size());
  + VectorOperations::AddInPlace(addresses, aggr.payload_size, result.size());
  }
  }
  