**How to reproduce**
Clickhouse version 21.5

```
cat /etc/clickhouse-server/users.xml
<?xml version="1.0"?>
<yandex>
    <!-- Profiles of settings. -->
    <profiles>
        <!-- Default settings. -->
        <default>
            <data_type_default_nullable>1</data_type_default_nullable>
            <load_balancing>random</load_balancing>
        </default>
....

2021.04.04 01:23:42.453678 [ 29048 ] {} <Error> Application: DB::Exception: Nested type Array(UInt64) cannot be inside Nullable type: Cannot attach table `system`.`crash_log` from metadata file /var/lib/clickhouse/metadata/system/crash_log.sql from query ATTACH TABLE system.crash_log (`event_date` Date, `event_time` DateTime, `timestamp_ns` UInt64, `signal` Int32, `thread_id` UInt64, `query_id` String, `trace` Array(UInt64), `trace_full` Array(String), `version` String, `revision` UInt32, `build_id` String) ENGINE = MergeTree ORDER BY (event_date, event_time) SETTINGS index_granularity = 8192: while loading database `system` from path /var/lib/clickhouse/metadata/system
```
else if (!query.replica_zk_path.empty())
    {
        getContext()->checkAccess(AccessType::SYSTEM_DROP_REPLICA);
        auto remote_replica_path = query.replica_zk_path  + "/replicas/" + query.replica;
        
        for (auto & elem : DatabaseCatalog::instance().getDatabases())
        {
            DatabasePtr & database = elem.second;
            for (auto iterator = database->getTablesIterator(getContext()); iterator->isValid(); iterator->next())
            {
                if (auto * storage_replicated = dynamic_cast<StorageReplicatedMergeTree *>(iterator->table().get()))
                {
                    StorageReplicatedMergeTree::Status status;
                    storage_replicated->getStatus(status);
                    if (status.zookeeper_path == query.replica_zk_path)
                        throw Exception("There is a local table " + storage_replicated->getStorageID().getNameForLogs() +
                                        ", which has the same table path in ZooKeeper. Please check the path in query. "
                                        "If you want to drop replica of this table, use `DROP TABLE` "
                                        "or `SYSTEM DROP REPLICA 'name' FROM db.table`", ErrorCodes::TABLE_WAS_NOT_DROPPED);
                }
            }
        }
        auto zookeeper = getContext()->getZooKeeper();
        bool looks_like_table_path = zookeeper->exists(query.replica_zk_path + "/replicas") ||
                                     zookeeper->exists(query.replica_zk_path + "/dropped");
        if (!looks_like_table_path)
            throw Exception("Specified path " + query.replica_zk_path + " does not look like a table path",
                            ErrorCodes::TABLE_WAS_NOT_DROPPED);
        if (zookeeper->exists(remote_replica_path + "/is_active"))
            throw Exception("Can't remove replica: " + query.replica + ", because it's active",