**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
```
const auto & final_column_name = col_decl.name;
                const auto tmp_column_name = final_column_name + "_tmp_alter" + toString(randomSeed());
                const auto * data_type_ptr = column_names_and_types.back().type.get();
                default_expr_list->children.emplace_back(
                    setAlias(addTypeConversionToAST(std::make_shared<ASTIdentifier>(tmp_column_name), data_type_ptr->getName()),
                        final_column_name));
                default_expr_list->children.emplace_back(
                    setAlias(
                        col_decl.default_expression->clone(),
                        tmp_column_name));
            }
            else
                default_expr_list->children.emplace_back(setAlias(col_decl.default_expression->clone(), col_decl.name));
        }
    }
    Block defaults_sample_block;
    
    if (!default_expr_list->children.empty())
        defaults_sample_block = validateColumnsDefaultsAndGetSampleBlock(default_expr_list, column_names_and_types, context_);
    ColumnsDescription res;
    auto name_type_it = column_names_and_types.begin();
    for (auto ast_it = columns_ast.children.begin(); ast_it != columns_ast.children.end(); ++ast_it, ++name_type_it)
    {
        ColumnDescription column;
        auto & col_decl = (*ast_it)->as<ASTColumnDeclaration &>();
        column.name = col_decl.name;
        if (col_decl.default_expression)
        {
            ASTPtr default_expr = col_decl.default_expression->clone();
            if (col_decl.type)