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
```
}
    
    
    for (size_t i = prepared_stages.size() - 1; i > 0; --i)
    {
        auto & stage = prepared_stages[i];
        ASTPtr all_asts = std::make_shared<ASTExpressionList>();
        for (const auto & ast : stage.filters)
            all_asts->children.push_back(ast);
        for (const auto & kv : stage.column_to_updated)
            all_asts->children.push_back(kv.second);
        
        for (const String & column : stage.output_columns)
            all_asts->children.push_back(std::make_shared<ASTIdentifier>(column));
        auto syntax_result = TreeRewriter(context).analyze(all_asts, all_columns, storage, metadata_snapshot);
        if (context->hasQueryContext())
            for (const auto & it : syntax_result->getScalars())
                context->getQueryContext()->addScalar(it.first, it.second);
        stage.analyzer = std::make_unique<ExpressionAnalyzer>(all_asts, syntax_result, context);
        ExpressionActionsChain & actions_chain = stage.expressions_chain;
        for (const auto & ast : stage.filters)
        {
            if (!actions_chain.steps.empty())
                actions_chain.addStep();
            stage.analyzer->appendExpression(actions_chain, ast, dry_run);
            stage.filter_column_names.push_back(ast->getColumnName());
        }
        if (!stage.column_to_updated.empty())
        {
            if (!actions_chain.steps.empty())