**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+
: DateTimeTransformImpl<DataTypeInt16, DataTypeDate, ToDateTransform8Or16Signed<Int16, UInt16>> {};
template <typename Name> struct ConvertImpl<DataTypeInt32, DataTypeDate, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeInt32, DataTypeDate, ToDateTransform32Or64Signed<Int32, UInt16>> {};
template <typename Name> struct ConvertImpl<DataTypeInt64, DataTypeDate, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeInt64, DataTypeDate, ToDateTransform32Or64Signed<Int64, UInt16>> {};
template <typename Name> struct ConvertImpl<DataTypeFloat32, DataTypeDate, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeFloat32, DataTypeDate, ToDateTransform32Or64Signed<Float32, UInt16>> {};
template <typename Name> struct ConvertImpl<DataTypeFloat64, DataTypeDate, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeFloat64, DataTypeDate, ToDateTransform32Or64Signed<Float64, UInt16>> {};
template <typename Name> struct ConvertImpl<DataTypeUInt32, DataTypeDate32, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeUInt32, DataTypeDate32, ToDate32Transform32Or64<UInt32, Int32>> {};
template <typename Name> struct ConvertImpl<DataTypeUInt64, DataTypeDate32, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeUInt64, DataTypeDate32, ToDate32Transform32Or64<UInt64, Int32>> {};
template <typename Name> struct ConvertImpl<DataTypeInt8, DataTypeDate32, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeInt8, DataTypeDate32, ToDate32Transform8Or16Signed<Int8, Int32>> {};
template <typename Name> struct ConvertImpl<DataTypeInt16, DataTypeDate32, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeInt16, DataTypeDate32, ToDate32Transform8Or16Signed<Int16, Int32>> {};
template <typename Name> struct ConvertImpl<DataTypeInt32, DataTypeDate32, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeInt32, DataTypeDate32, ToDate32Transform32Or64Signed<Int32, Int32>> {};
template <typename Name> struct ConvertImpl<DataTypeInt64, DataTypeDate32, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeInt64, DataTypeDate32, ToDate32Transform32Or64Signed<Int64, Int32>> {};
template <typename Name> struct ConvertImpl<DataTypeFloat32, DataTypeDate32, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeFloat32, DataTypeDate32, ToDate32Transform32Or64Signed<Float32, Int32>> {};
template <typename Name> struct ConvertImpl<DataTypeFloat64, DataTypeDate32, Name, ConvertDefaultBehaviorTag>
    : DateTimeTransformImpl<DataTypeFloat64, DataTypeDate32, ToDate32Transform32Or64Signed<Float64, Int32>> {};
template <typename FromType, typename ToType>
struct ToDateTimeTransform64
{
    static constexpr auto name = "toDateTime";
    static inline NO_SANITIZE_UNDEFINED ToType execute(const FromType & from, const DateLUTImpl &)