**How to reproduce**
Clickhouse server 20.13.1.5273
```
CREATE TABLE default.test
(
`key` UInt32,
`ts` DateTime CODEC(DoubleDelta, LZ4),
`db_time` DateTime DEFAULT now() COMMENT 'spout-ignore' CODEC(DoubleDelta, LZ4)
)
ENGINE = MergeTree
PARTITION BY toStartOfTenMinutes(db_time)
ORDER BY (key, ts)
TTL db_time + toIntervalHour(3)
SETTINGS index_granularity = 8192, merge_with_ttl_timeout = 3600, min_rows_for_compact_part = 1000000, min_bytes_for_compact_part = 200000000, in_memory_parts_enable_wal = 0;


INSERT INTO test(key, ts) SELECT number % 1000, now() + intDiv(number,1000) FROM numbers(500);

SELECT * FROM test;
500 rows in set. Elapsed: 0.003 sec.

DETACH TABLE test;

ATTACH TABLE test;

SELECT * FROM test;

0 rows in set. Elapsed: 0.002 sec.
```

**Expected behavior**
Clickhouse would flush parts on disk.
const StorageMetadataPtr & metadata_snapshot, String * , TableLockHolder & ,
    std::unique_lock<std::mutex> & currently_processing_in_background_mutex_lock,
    bool & were_some_mutations_for_some_parts_skipped)
{
    size_t max_ast_elements = getContext()->getSettingsRef().max_expanded_ast_elements;
    auto future_part = std::make_shared<FutureMergedMutatedPart>();
    if (storage_settings.get()->assign_part_uuids)
        future_part->uuid = UUIDHelpers::generateV4();
    CurrentlyMergingPartsTaggerPtr tagger;
    if (current_mutations_by_version.empty())
        return {};
    size_t max_source_part_size = merger_mutator.getMaxSourcePartSizeForMutation();
    if (max_source_part_size == 0)
    {
        LOG_DEBUG(
            log,
            "Not enough idle threads to apply mutations at the moment. See settings 'number_of_free_entries_in_pool_to_execute_mutation' "
            "and 'background_pool_size'");
        return {};
    }
    auto mutations_end_it = current_mutations_by_version.end();
    for (const auto & part : getDataPartsVector())
    {
        if (currently_merging_mutating_parts.count(part))
            continue;
        auto mutations_begin_it = current_mutations_by_version.upper_bound(getUpdatedDataVersion(part, currently_processing_in_background_mutex_lock));
        if (mutations_begin_it == mutations_end_it)
            continue;