**How to reproduce**
Clickhouse version 21.2-21.3

```
SELECT x
FROM
(
    SELECT 1 AS x
    UNION DISTINCT
    SELECT 1
)
LIMIT 1

Query id: b82bbb8d-dea9-4f1c-9a2f-5b0e9b6c2422


0 rows in set. Elapsed: 0.002 sec.

Received exception from server (version 21.2.3):
Code: 49. DB::Exception: Received from localhost:9000. DB::Exception: Bad cast from type DB::ASTSelectWithUnionQuery to DB::ASTSelectQuery.
```


const WindowDescription & _full)
{
    const auto & prefix = _prefix.full_sort_description;
    const auto & full = _full.full_sort_description;
    if (prefix.size() > full.size())
    {
        return false;
    }
    for (size_t i = 0; i < prefix.size(); ++i)
    {
        if (full[i] != prefix[i])
        {
            return false;
        }
    }
    return true;
}
void InterpreterSelectQuery::executeWindow(QueryPlan & query_plan)