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 (!select_interpreter)
        select_interpreter = std::make_unique<InterpreterSelectQuery>(mutation_ast, context, storage, metadata_snapshot, select_limits);
    const Settings & settings = context->getSettingsRef();
    
    
    if (startsWith(storage->getName(), "Replicated") && !settings.allow_nondeterministic_mutations)
    {
        for (const auto & command : commands)
        {
            const auto nondeterministic_func_name = findFirstNonDeterministicFunctionName(command, context);
            if (nondeterministic_func_name)
                throw Exception(
                    "ALTER UPDATE/ALTER DELETE statements must use only deterministic functions! "
                    "Function '" + *nondeterministic_func_name + "' is non-deterministic",
                    ErrorCodes::BAD_ARGUMENTS);
        }
    }
    QueryPlan plan;
    select_interpreter->buildQueryPlan(plan);
    auto pipeline = addStreamsForLaterStages(stages, plan);
}
BlockInputStreamPtr MutationsInterpreter::execute()