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
```
new_data_part->index_granularity_info = source_part->index_granularity_info;
    new_data_part->setColumns(getColumnsForNewDataPart(source_part, updated_header, storage_columns, for_file_renames));
    new_data_part->partition.assign(source_part->partition);
    auto disk = new_data_part->volume->getDisk();
    String new_part_tmp_path = new_data_part->getFullRelativePath();
    SyncGuardPtr sync_guard;
    if (data.getSettings()->fsync_part_directory)
        sync_guard = disk->getDirectorySyncGuard(new_part_tmp_path);
    
    auto mrk_extension = source_part->index_granularity_info.is_adaptive ? getAdaptiveMrkExtension(new_data_part->getType())
                                                                         : getNonAdaptiveMrkExtension();
    bool need_sync = needSyncPart(source_part->rows_count, source_part->getBytesOnDisk(), *data_settings);
    bool need_remove_expired_values = false;
    if (in && shouldExecuteTTL(metadata_snapshot, in->getHeader().getNamesAndTypesList().getNames(), commands_for_part))
        need_remove_expired_values = true;
    
    
    if (!isWidePart(source_part)
        || (mutation_kind == MutationsInterpreter::MutationKind::MUTATE_OTHER && interpreter && interpreter->isAffectingAllColumns()))
    {
        disk->createDirectories(new_part_tmp_path);
        
        
        
        
        
        auto compression_codec = data.getCompressionCodecForPart(source_part->getBytesOnDisk(), source_part->ttl_infos, time_of_mutation);
        auto part_indices = getIndicesForNewDataPart(metadata_snapshot->getSecondaryIndices(), for_file_renames);
        auto part_projections = getProjectionsForNewDataPart(metadata_snapshot->getProjections(), for_file_renames);