**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+
}
                else
                {
                    for (size_t i = 0; i < size; ++i)
                        out_data[i] = result_type.getValue(col->getDataAt(i));
                }
                return res;
            }
            else
                throw Exception{"Unexpected column " + first_col->getName() + " as first argument of function " + function_name,
                    ErrorCodes::LOGICAL_ERROR};
        };
    }
    static WrapperType createIdentityWrapper(const DataTypePtr &)
    {
        return [] (ColumnsWithTypeAndName & arguments, const DataTypePtr &, const ColumnNullable *, size_t )
        {
            return arguments.front().column;
        };
    }
    static WrapperType createNothingWrapper(const IDataType * to_type)
    {
        ColumnPtr res = to_type->createColumnConstWithDefaultValue(1);
        return [res] (ColumnsWithTypeAndName &, const DataTypePtr &, const ColumnNullable *, size_t input_rows_count)
        {
            
            return res->cloneResized(input_rows_count)->convertToFullColumnIfConst();
        };
    }
    WrapperType prepareUnpackDictionaries(const DataTypePtr & from_type, const DataTypePtr & to_type) const