**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 DataPartPtr & part,
    std::unique_lock<std::mutex> & currently_processing_in_background_mutex_lock) const
{
    auto it = current_mutations_by_version.upper_bound(getUpdatedDataVersion(part, currently_processing_in_background_mutex_lock));
    if (it == current_mutations_by_version.begin())
        return 0;
    --it;
    return it->first;
}
size_t StorageMergeTree::clearOldMutations(bool truncate)
{
    const auto settings = getSettings();
    if (!truncate && !settings->finished_mutations_to_keep)
        return 0;
    std::vector<MergeTreeMutationEntry> mutations_to_delete;
    {
        std::unique_lock<std::mutex> lock(currently_processing_in_background_mutex);
        if (!truncate && current_mutations_by_version.size() <= settings->finished_mutations_to_keep)
            return 0;
        auto end_it = current_mutations_by_version.end();
        auto begin_it = current_mutations_by_version.begin();
        size_t to_delete_count = std::distance(begin_it, end_it);
        if (!truncate)
        {
            if (std::optional<Int64> min_version = getMinPartDataVersion())
                end_it = current_mutations_by_version.upper_bound(*min_version);
            size_t done_count = std::distance(begin_it, end_it);
            if (done_count <= settings->finished_mutations_to_keep)
                return 0;
            auto part_versions_with_names = getSortedPartVersionsWithNames(lock);