**Describe what's wrong**

```sql
SELECT toTypeName(s), toString(s) FROM
(
 SELECT toFixedString('',32) AS s 
 UNION ALL
 SELECT null AS s 
)
```

this query works in all versions from 19.17 to 21.8, but stop works after 21.9+ 

https://fiddle.clickhouse.com/7bd65b36-a6e6-470a-8bdc-4c98a33ff453
21.8 works

https://fiddle.clickhouse.com/9e40a424-4027-4c7f-bd41-b20935ae9129
21.9 doesn't work
```
Received exception from server (version 21.9.6):
Code: 44. DB::Exception: Received from localhost:9000. DB::Exception: Illegal column Nullable(FixedString(32)) of first argument of function toString. (ILLEGAL_COLUMN)
```

this query works in all versions

```sql
SELECT toTypeName(s), toString(s) FROM
(
 SELECT '' AS s 
 UNION ALL
 SELECT null AS s 
)
```
https://fiddle.clickhouse.com/4f810f03-1644-4eb7-b696-0341b1bbdbc4


**Does it reproduce on recent release?**
Yes, reproduce in all releases 21.9+
{
                serialization->serializeText(col_from, i, write_buffer, format_settings);
                write_helper.rowWritten();
            }
            write_helper.finalize();
        }
        if (result_type->isNullable() && null_map)
            return ColumnNullable::create(std::move(col_to), std::move(null_map));
        return col_to;
    }
};
/** Conversion of time_t to UInt16, Int32, UInt32
  */
template <typename DataType>
void convertFromTime(typename DataType::FieldType & x, time_t & time)
{
    x = time;
}
template <>
inline void convertFromTime<DataTypeDate>(DataTypeDate::FieldType & x, time_t & time)
{
    if (unlikely(time < 0))
        x = 0;
    else if (unlikely(time > 0xFFFF))
        x = 0xFFFF;
    else
        x = time;
}
template <>
inline void convertFromTime<DataTypeDate32>(DataTypeDate32::FieldType & x, time_t & time)