**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+
DataTypeDateTime, NameParseDateTimeBestEffort, ConvertFromStringExceptionMode::Throw, ConvertFromStringParsingMode::BestEffort>;
using FunctionParseDateTimeBestEffortOrZero = FunctionConvertFromString<
    DataTypeDateTime, NameParseDateTimeBestEffortOrZero, ConvertFromStringExceptionMode::Zero, ConvertFromStringParsingMode::BestEffort>;
using FunctionParseDateTimeBestEffortOrNull = FunctionConvertFromString<
    DataTypeDateTime, NameParseDateTimeBestEffortOrNull, ConvertFromStringExceptionMode::Null, ConvertFromStringParsingMode::BestEffort>;
using FunctionParseDateTimeBestEffortUS = FunctionConvertFromString<
    DataTypeDateTime, NameParseDateTimeBestEffortUS, ConvertFromStringExceptionMode::Throw, ConvertFromStringParsingMode::BestEffortUS>;
using FunctionParseDateTimeBestEffortUSOrZero = FunctionConvertFromString<
    DataTypeDateTime, NameParseDateTimeBestEffortUSOrZero, ConvertFromStringExceptionMode::Zero, ConvertFromStringParsingMode::BestEffortUS>;
using FunctionParseDateTimeBestEffortUSOrNull = FunctionConvertFromString<
    DataTypeDateTime, NameParseDateTimeBestEffortUSOrNull, ConvertFromStringExceptionMode::Null, ConvertFromStringParsingMode::BestEffortUS>;
using FunctionParseDateTime32BestEffort = FunctionConvertFromString<
    DataTypeDateTime, NameParseDateTime32BestEffort, ConvertFromStringExceptionMode::Throw, ConvertFromStringParsingMode::BestEffort>;
using FunctionParseDateTime32BestEffortOrZero = FunctionConvertFromString<
    DataTypeDateTime, NameParseDateTime32BestEffortOrZero, ConvertFromStringExceptionMode::Zero, ConvertFromStringParsingMode::BestEffort>;
using FunctionParseDateTime32BestEffortOrNull = FunctionConvertFromString<
    DataTypeDateTime, NameParseDateTime32BestEffortOrNull, ConvertFromStringExceptionMode::Null, ConvertFromStringParsingMode::BestEffort>;
using FunctionParseDateTime64BestEffort = FunctionConvertFromString<
    DataTypeDateTime64, NameParseDateTime64BestEffort, ConvertFromStringExceptionMode::Throw, ConvertFromStringParsingMode::BestEffort>;
using FunctionParseDateTime64BestEffortOrZero = FunctionConvertFromString<
    DataTypeDateTime64, NameParseDateTime64BestEffortOrZero, ConvertFromStringExceptionMode::Zero, ConvertFromStringParsingMode::BestEffort>;
using FunctionParseDateTime64BestEffortOrNull = FunctionConvertFromString<
    DataTypeDateTime64, NameParseDateTime64BestEffortOrNull, ConvertFromStringExceptionMode::Null, ConvertFromStringParsingMode::BestEffort>;
using FunctionParseDateTime64BestEffortUS = FunctionConvertFromString<
    DataTypeDateTime64, NameParseDateTime64BestEffortUS, ConvertFromStringExceptionMode::Throw, ConvertFromStringParsingMode::BestEffortUS>;
using FunctionParseDateTime64BestEffortUSOrZero = FunctionConvertFromString<
    DataTypeDateTime64, NameParseDateTime64BestEffortUSOrZero, ConvertFromStringExceptionMode::Zero, ConvertFromStringParsingMode::BestEffortUS>;
using FunctionParseDateTime64BestEffortUSOrNull = FunctionConvertFromString<
    DataTypeDateTime64, NameParseDateTime64BestEffortUSOrNull, ConvertFromStringExceptionMode::Null, ConvertFromStringParsingMode::BestEffortUS>;
class ExecutableFunctionCast : public IExecutableFunction