message: Fix mistake in ClusterTree::insert
diff: @@ -1937,13 +1937,8 @@ Obj ClusterTree::insert(ObjKey k, const FieldValues& values)
  index->insert(k, init_value.get<Timestamp>());
  }
  break;
  - case col_type_Decimal:
  - if (init_value.is_null()) {
  - index->insert(k, ArrayDecimal128::default_value(nullable));
  - }
  - else {
  - index->insert(k, init_value.get<Timestamp>());
  - }
  + case col_type_ObjectId:
  + index->insert(k, init_value.get<ObjectId>());
  break;
  default:
  break;
  