**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:`

result = std::move(dictionary_get_result_column);
            }
            else
                result = ColumnNullable::create(std::move(dictionary_get_result_column), std::move(is_key_in_dictionary_column_mutable));
        }
        return result;
    }
    static void addNullMap(PaddedPODArray<UInt8> & null_map, PaddedPODArray<UInt8> & null_map_to_add)
    {
        assert(null_map.size() == null_map_to_add.size());
        for (size_t i = 0; i < null_map.size(); ++i)
            null_map[i] = null_map[i] || null_map_to_add[i];
    }
    static ColumnsWithTypeAndName filterAttributeNameArgumentForDictHas(const ColumnsWithTypeAndName & arguments)
    {
        ColumnsWithTypeAndName dict_has_arguments;
        dict_has_arguments.reserve(arguments.size() - 1);
        size_t attribute_name_argument_index = 1;
        for (size_t i = 0; i < arguments.size(); ++i)
        {
            if (i == attribute_name_argument_index)
                continue;
            dict_has_arguments.emplace_back(arguments[i]);
        }
        return dict_has_arguments;
    }
    const FunctionDictGetNoType<DictionaryGetFunctionType::get> dictionary_get_func_impl;
    const FunctionDictHas dictionary_has_func_impl;
};
class FunctionDictGetHierarchy final : public IFunction