mongos returns no results for $documents if the database doesn't exist

db.aggregate([{$documents: [{_id: 1}, {_id: 2}]}]);

    // If the routing table is valid, we obtain a reference to it. If the table is not valid, then

    // either the database does not exist, or there are no shards in the cluster. In the latter

    // case, we always return an empty cursor. In the former case, if the requested aggregation is a

    // $changeStream, we allow the operation to continue so that stream cursors can be established

    // on the given namespace before the database or collection is actually created. If the database

    // does not exist and this is not a $changeStream, then we return an empty cursor.

    boost::optional<ChunkManager> cm;

    auto executionNsRoutingInfoStatus =

        sharded_agg_helpers::getExecutionNsRoutingInfo(opCtx, namespaces.executionNss);

    if (!executionNsRoutingInfoStatus.isOK()) {

        if (liteParsedPipeline.startsWithCollStats()) {

            uassertStatusOKWithContext(executionNsRoutingInfoStatus,

                                       "Unable to retrieve information for $collStats stage");

        }

    }

    if (executionNsRoutingInfoStatus.isOK()) {

        cm = std::move(executionNsRoutingInfoStatus.getValue());

    } else if (!(hasChangeStream &&

                 executionNsRoutingInfoStatus == ErrorCodes::NamespaceNotFound)) {

        appendEmptyResultSetWithStatus(

            opCtx, namespaces.requestedNss, executionNsRoutingInfoStatus.getStatus(), result);

        return Status::OK();

    }