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
```
MergeTreeData::DataPartPtr source_part, const MutationCommands & commands_for_removes, const String & mrk_extension)
{
    
    std::map<String, size_t> stream_counts;
    for (const NameAndTypePair & column : source_part->getColumns())
    {
        auto serialization = source_part->getSerializationForColumn(column);
        serialization->enumerateStreams(
            [&](const ISerialization::SubstreamPath & substream_path)
            {
                ++stream_counts[ISerialization::getFileNameForStream(column, substream_path)];
            },
            {});
    }
    NameToNameVector rename_vector;
    
    for (const auto & command : commands_for_removes)
    {
        if (command.type == MutationCommand::Type::DROP_INDEX)
        {
            if (source_part->checksums.has(INDEX_FILE_PREFIX + command.column_name + ".idx"))
            {
                rename_vector.emplace_back(INDEX_FILE_PREFIX + command.column_name + ".idx", "");
                rename_vector.emplace_back(INDEX_FILE_PREFIX + command.column_name + mrk_extension, "");
            }
        }
        else if (command.type == MutationCommand::Type::DROP_PROJECTION)
        {
            if (source_part->checksums.has(command.column_name + ".proj"))
                rename_vector.emplace_back(command.column_name + ".proj", "");