version 21.5.5.12 (official build)

I'm trying to change data type for a column that is used in the TTL expression.
It works well when the table is empty.
When the table is not empty, the mutation fails.
As a result the table ends up in an inconsistent state.

```
create table test
(
InsertionDateTime DateTime,
TTLDays Int32 DEFAULT CAST(365, 'Int32')
)
Engine=MergeTree()
order by tuple()
TTL InsertionDateTime + toIntervalDay(TTLDays);

Ok.

insert into test values (now(), 23);

Ok.

ALTER TABLE test modify column TTLDays Int16 DEFAULT CAST(365, 'Int16');

Code: 341, e.displayText() = DB::Exception: Exception happened during execution of mutation 'mutation_2.txt' with part 'all_1_1_0' reason: 'Code: 10, e.displayText() = DB::Exception: Not found column InsertionDateTime in block. There are only columns: TTLDays (version 21.5.5.12 (official build))'. This error maybe retryable or not. In case of unretryable error, mutation can be killed with KILL MUTATION query (version 21.5.5.12 (official build)) [DB Errorcode=341]

insert into test values (now(), 23);

Ok.

select table, column, type, sum(rows) rows, sum(column_bytes_on_disk) on_disk
from system.parts_columns where column like 'TTLDays'
group by database, table, column, type

table | column  | type  | rows | on_disk
------+---------+-------+------+--------
test  | TTLDays | Int32 |    1 |      86
test  | TTLDays | Int16 |    1 |      84
```
parts, sum_input_rows_upper_bound, gathering_columns, deduplicate, need_remove_expired_values, merging_params);
    merge_entry->merge_algorithm.store(chosen_merge_algorithm, std::memory_order_relaxed);
    LOG_DEBUG(log, "Selected MergeAlgorithm: {}", toString(chosen_merge_algorithm));
    
    
    
    
    
    auto compression_codec = data.getCompressionCodecForPart(merge_entry->total_size_bytes_compressed, new_data_part->ttl_infos, time_of_merge);
    auto tmp_disk = context->getTemporaryVolume()->getDisk();
    String rows_sources_file_path;
    std::unique_ptr<WriteBufferFromFileBase> rows_sources_uncompressed_write_buf;
    std::unique_ptr<WriteBuffer> rows_sources_write_buf;
    std::optional<ColumnSizeEstimator> column_sizes;
    SyncGuardPtr sync_guard;
    if (chosen_merge_algorithm == MergeAlgorithm::Vertical)
    {
        tmp_disk->createDirectories(new_part_tmp_path);
        rows_sources_file_path = new_part_tmp_path + "rows_sources";
        rows_sources_uncompressed_write_buf = tmp_disk->writeFile(rows_sources_file_path);
        rows_sources_write_buf = std::make_unique<CompressedWriteBuffer>(*rows_sources_uncompressed_write_buf);
        MergeTreeData::DataPart::ColumnToSize merged_column_to_size;
        for (const MergeTreeData::DataPartPtr & part : parts)
            part->accumulateColumnSizes(merged_column_to_size);
        column_sizes = ColumnSizeEstimator(merged_column_to_size, merging_column_names, gathering_column_names);
        if (data.getSettings()->fsync_part_directory)
            sync_guard = disk->getDirectorySyncGuard(new_part_tmp_path);
    }
    else
    {