**Describe the unexpected behaviour**
If Null being passed as dictionary key, dictGetOrDefault returns null instead of default value.

**How to reproduce**
Clickhouse version 21.5, 21.1, 20.8

```

CREATE VIEW dict_null_source AS SELECT 1 as key, 1 as val;
CREATE DICTIONARY dict_null (key UInt64, val UInt32) PRIMARY KEY key SOURCE(CLICKHOUSE(host 'localhost' user 'default' table 'dict_null_source' ))LAYOUT(FLAT)LIFETIME(300)


SELECT dictGetOrDefault('default.dict_null', 'val', CAST(NULL, 'Nullable(UInt64)'), 0) AS val

Query id: 79518a8e-b439-4d08-a0b2-85e4b3ef99eb

┌──val─┐
│ ᴺᵁᴸᴸ │
└──────┘
```

**Additional context**
```

SELECT dictGetOrDefault('default.dict_null', 'val', CAST(1, 'UInt64'))

Query id: 71ec76a1-fb61-4641-9145-79c6bfffd490


0 rows in set. Elapsed: 0.001 sec.

Received exception from server (version 21.5.1):
Code: 42. DB::Exception: Received from localhost:9000. DB::Exception: Wrong argument count for function dictGetOrDefault: While processing dictGetOrDefault('default.dict_null', 'val', CAST(1, 'UInt64')).

```

Error message in 21.1 was better:  `Number of arguments for function dictGetOrDefault doesn't match: passed 3, should be 4:`

private:
    size_t getNumberOfArguments() const override { return 0; }
    bool isVariadic() const override { return true; }
    bool useDefaultImplementationForConstants() const override { return true; }
    bool useDefaultImplementationForNulls() const override { return false; }
    bool isDeterministic() const override { return false; }
    ColumnNumbers getArgumentsThatAreAlwaysConstant() const override { return {0, 1}; }
    bool isInjective(const ColumnsWithTypeAndName & sample_columns) const override
    {
        return dictionary_get_func_impl.isInjective(sample_columns);
    }
    DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const override
    {
        auto result_type = dictionary_get_func_impl.getReturnTypeImpl(arguments);
        WhichDataType result_data_type(result_type);
        if (result_data_type.isTuple())
        {
            const auto & data_type_tuple = static_cast<const DataTypeTuple &>(*result_type);
            auto elements_types_copy = data_type_tuple.getElements();
            for (auto & element_type : elements_types_copy)
                element_type = makeNullable(element_type);
            result_type = std::make_shared<DataTypeTuple>(elements_types_copy, data_type_tuple.getElementNames());
        }
        else
            result_type = makeNullable(result_type);
        return result_type;
    }
    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t input_rows_count) const override