Bad cast from type DB::IColumn* to DB::ColumnFixedString*.

```
/4/ :) SELECT if(number % 2, toFixedString(toString(number), 2), toFixedString(toString(-number), 65535)) FROM system.numbers LIMIT 10

Code: 368. DB::Exception: Received from localhost:9000. DB::Exception: Bad cast from type DB::IColumn* to DB::ColumnFixedString*. Stack trace:
```