**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+
struct NameToDecimal32OrZero { static constexpr auto name = "toDecimal32OrZero"; };
struct NameToDecimal64OrZero { static constexpr auto name = "toDecimal64OrZero"; };
struct NameToDecimal128OrZero { static constexpr auto name = "toDecimal128OrZero"; };
struct NameToDecimal256OrZero { static constexpr auto name = "toDecimal256OrZero"; };
struct NameToUUIDOrZero { static constexpr auto name = "toUUIDOrZero"; };
using FunctionToUInt8OrZero = FunctionConvertFromString<DataTypeUInt8, NameToUInt8OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToUInt16OrZero = FunctionConvertFromString<DataTypeUInt16, NameToUInt16OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToUInt32OrZero = FunctionConvertFromString<DataTypeUInt32, NameToUInt32OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToUInt64OrZero = FunctionConvertFromString<DataTypeUInt64, NameToUInt64OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToUInt128OrZero = FunctionConvertFromString<DataTypeUInt128, NameToUInt128OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToUInt256OrZero = FunctionConvertFromString<DataTypeUInt256, NameToUInt256OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToInt8OrZero = FunctionConvertFromString<DataTypeInt8, NameToInt8OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToInt16OrZero = FunctionConvertFromString<DataTypeInt16, NameToInt16OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToInt32OrZero = FunctionConvertFromString<DataTypeInt32, NameToInt32OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToInt64OrZero = FunctionConvertFromString<DataTypeInt64, NameToInt64OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToInt128OrZero = FunctionConvertFromString<DataTypeInt128, NameToInt128OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToInt256OrZero = FunctionConvertFromString<DataTypeInt256, NameToInt256OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToFloat32OrZero = FunctionConvertFromString<DataTypeFloat32, NameToFloat32OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToFloat64OrZero = FunctionConvertFromString<DataTypeFloat64, NameToFloat64OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToDateOrZero = FunctionConvertFromString<DataTypeDate, NameToDateOrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToDate32OrZero = FunctionConvertFromString<DataTypeDate32, NameToDate32OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToDateTimeOrZero = FunctionConvertFromString<DataTypeDateTime, NameToDateTimeOrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToDateTime64OrZero = FunctionConvertFromString<DataTypeDateTime64, NameToDateTime64OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToDecimal32OrZero = FunctionConvertFromString<DataTypeDecimal<Decimal32>, NameToDecimal32OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToDecimal64OrZero = FunctionConvertFromString<DataTypeDecimal<Decimal64>, NameToDecimal64OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToDecimal128OrZero = FunctionConvertFromString<DataTypeDecimal<Decimal128>, NameToDecimal128OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToDecimal256OrZero = FunctionConvertFromString<DataTypeDecimal<Decimal256>, NameToDecimal256OrZero, ConvertFromStringExceptionMode::Zero>;
using FunctionToUUIDOrZero = FunctionConvertFromString<DataTypeUUID, NameToUUIDOrZero, ConvertFromStringExceptionMode::Zero>;
struct NameToUInt8OrNull { static constexpr auto name = "toUInt8OrNull"; };
struct NameToUInt16OrNull { static constexpr auto name = "toUInt16OrNull"; };