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->select()->children.empty())
        select->select()->children.push_back(std::make_shared<ASTLiteral>(Field(0)));
    if (!prepared_stages[0].filters.empty())
    {
        ASTPtr where_expression;
        if (prepared_stages[0].filters.size() == 1)
            where_expression = prepared_stages[0].filters[0];
        else
        {
            auto coalesced_predicates = std::make_shared<ASTFunction>();
            coalesced_predicates->name = "and";
            coalesced_predicates->arguments = std::make_shared<ASTExpressionList>();
            coalesced_predicates->children.push_back(coalesced_predicates->arguments);
            coalesced_predicates->arguments->children = prepared_stages[0].filters;
            where_expression = std::move(coalesced_predicates);
        }
        select->setExpression(ASTSelectQuery::Expression::WHERE, std::move(where_expression));
    }
    return select;
}
QueryPipelinePtr MutationsInterpreter::addStreamsForLaterStages(const std::vector<Stage> & prepared_stages, QueryPlan & plan) const
{
    for (size_t i_stage = 1; i_stage < prepared_stages.size(); ++i_stage)
    {
        const Stage & stage = prepared_stages[i_stage];
        for (size_t i = 0; i < stage.expressions_chain.steps.size(); ++i)
        {
            const auto & step = stage.expressions_chain.steps[i];
            if (i < stage.filter_column_names.size())
            {