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
```
{
            if (column.default_desc.kind == ColumnDefaultKind::Materialized)
            {
                auto query = column.default_desc.expression->clone();
                auto syntax_result = TreeRewriter(context).analyze(query, all_columns);
                for (const String & dependency : syntax_result->requiredSourceColumns())
                {
                    if (updated_columns.count(dependency))
                        column_to_affected_materialized[dependency].push_back(column.name);
                }
            }
        }
        validateUpdateColumns(storage, metadata_snapshot, updated_columns, column_to_affected_materialized);
    }
    
    auto dependencies = getAllColumnDependencies(metadata_snapshot, updated_columns);
    
    for (auto & command : commands)
    {
        if (command.type == MutationCommand::DELETE)
        {
            mutation_kind.set(MutationKind::MUTATE_OTHER);
            if (stages.empty() || !stages.back().column_to_updated.empty())
                stages.emplace_back(context);
            auto negated_predicate = makeASTFunction("isZeroOrNull", getPartitionAndPredicateExpressionForMutationCommand(command));
            stages.back().filters.push_back(negated_predicate);
        }
        else if (command.type == MutationCommand::UPDATE)
        {
            mutation_kind.set(MutationKind::MUTATE_OTHER);