**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+
static UInt64 divideByRangeOfType(UInt64 x)
    {
        if constexpr (sizeof(T) < sizeof(UInt64))
            return x >> (sizeof(T) * 8);
        else
            return 0;
    }
    static IFunction::Monotonicity get(const IDataType & type, const Field & left, const Field & right)
    {
        if (!type.isValueRepresentedByNumber())
            return {};
        
        
        if (checkAndGetDataType<DataTypeNumber<T>>(&type) ||
            checkAndGetDataType<DataTypeEnum<T>>(&type))
            return { .is_monotonic = true, .is_always_monotonic = true };
        
        
        if constexpr (std::is_floating_point_v<T>)
            return { .is_monotonic = true, .is_always_monotonic = true };
        
        if (WhichDataType(type).isFloat())
        {
            if (left.isNull() || right.isNull())
                return {};
            Float64 left_float = left.get<Float64>();
            Float64 right_float = right.get<Float64>();
            if (left_float >= static_cast<Float64>(std::numeric_limits<T>::min())
                && left_float <= static_cast<Float64>(std::numeric_limits<T>::max())
                && right_float >= static_cast<Float64>(std::numeric_limits<T>::min())