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
```
{
                bool was_renamed = false;
                bool was_removed = removed_columns.count(it->name);
                
                for (const auto & [rename_to, rename_from] : renamed_columns_to_from)
                {
                    if (rename_from == it->name)
                    {
                        was_renamed = true;
                        break;
                    }
                }
                
                
                if (renamed_columns_to_from.count(it->name) && !was_renamed && !was_removed)
                    throw Exception(
                        ErrorCodes::LOGICAL_ERROR,
                        "Incorrect mutation commands, trying to rename column {} to {}, but part {} already has column {}", renamed_columns_to_from[it->name], it->name, source_part->name, it->name);
                
                
                if (!renamed_columns_to_from.count(it->name) && (was_renamed || was_removed))
                    it = storage_columns.erase(it);
                else
                    ++it;
            }
        }
    }
    return storage_columns;
}
MergeTreeIndices MergeTreeDataMergerMutator::getIndicesForNewDataPart(