**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:`

if (!tuple_column)
                    throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
                        "Wrong argument for function ({}) default values column must be tuple", getName());
                if (tuple_column->tupleSize() != attribute_names.size())
                    throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
                        "Wrong argument for function ({}) default values tuple column must contain same column size as requested attributes",
                        getName());
                default_cols = tuple_column->getColumnsCopy();
            }
            else
                default_cols.emplace_back(result);
        }
        else
        {
            for (size_t i = 0; i < attribute_names.size(); ++i)
                default_cols.emplace_back(nullptr);
        }
        ColumnPtr result;
        const ColumnWithTypeAndName & key_col_with_type = arguments[2];
        const auto key_column = key_col_with_type.column;
        if (dictionary_key_type == DictionaryKeyType::simple)
        {
            if (!WhichDataType(key_col_with_type.type).isUInt64())
                 throw Exception(
                     ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
                     "Third argument of function ({}) must be uint64 when dictionary is simple. Actual type ({}).",
                     getName(),
                     key_col_with_type.type->getName());
            if (attribute_names.size() > 1)
            {