**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+
bool useDefaultImplementationForNothing() const override { return false; }
    bool useDefaultImplementationForConstants() const override { return true; }
    bool useDefaultImplementationForLowCardinalityColumns() const override { return false; }
    ColumnNumbers getArgumentsThatAreAlwaysConstant() const override { return {1}; }
private:
    WrapperType wrapper_function;
    const char * name;
    std::optional<Diagnostic> diagnostic;
};
struct CastName { static constexpr auto name = "CAST"; };
struct CastInternalName { static constexpr auto name = "_CAST"; };
enum class CastType
{
    nonAccurate,
    accurate,
    accurateOrNull
};
class FunctionCastBase : public IFunctionBase
{
public:
    using MonotonicityForRange = std::function<Monotonicity(const IDataType &, const Field &, const Field &)>;
    using Diagnostic = ExecutableFunctionCast::Diagnostic;
};
template <typename FunctionName>
class FunctionCast final : public FunctionCastBase
{
public:
    using WrapperType = std::function<ColumnPtr(ColumnsWithTypeAndName &, const DataTypePtr &, const ColumnNullable *, size_t)>;
    FunctionCast(const char * cast_name_