**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:`

struct NameDictGetDateTime { static constexpr auto name = "dictGetDateTime"; };
struct NameDictGetUUID { static constexpr auto name = "dictGetUUID"; };
struct NameDictGetDecimal32 { static constexpr auto name = "dictGetDecimal32"; };
struct NameDictGetDecimal64 { static constexpr auto name = "dictGetDecimal64"; };
struct NameDictGetDecimal128 { static constexpr auto name = "dictGetDecimal128"; };
struct NameDictGetString { static constexpr auto name = "dictGetString"; };
using FunctionDictGetUInt8 = FunctionDictGet<DataTypeUInt8, NameDictGetUInt8>;
using FunctionDictGetUInt16 = FunctionDictGet<DataTypeUInt16, NameDictGetUInt16>;
using FunctionDictGetUInt32 = FunctionDictGet<DataTypeUInt32, NameDictGetUInt32>;
using FunctionDictGetUInt64 = FunctionDictGet<DataTypeUInt64, NameDictGetUInt64>;
using FunctionDictGetInt8 = FunctionDictGet<DataTypeInt8, NameDictGetInt8>;
using FunctionDictGetInt16 = FunctionDictGet<DataTypeInt16, NameDictGetInt16>;
using FunctionDictGetInt32 = FunctionDictGet<DataTypeInt32, NameDictGetInt32>;
using FunctionDictGetInt64 = FunctionDictGet<DataTypeInt64, NameDictGetInt64>;
using FunctionDictGetFloat32 = FunctionDictGet<DataTypeFloat32, NameDictGetFloat32>;
using FunctionDictGetFloat64 = FunctionDictGet<DataTypeFloat64, NameDictGetFloat64>;
using FunctionDictGetDate = FunctionDictGet<DataTypeDate, NameDictGetDate>;
using FunctionDictGetDateTime = FunctionDictGet<DataTypeDateTime, NameDictGetDateTime>;
using FunctionDictGetUUID = FunctionDictGet<DataTypeUUID, NameDictGetUUID>;
using FunctionDictGetDecimal32 = FunctionDictGet<DataTypeDecimal<Decimal32>, NameDictGetDecimal32>;
using FunctionDictGetDecimal64 = FunctionDictGet<DataTypeDecimal<Decimal64>, NameDictGetDecimal64>;
using FunctionDictGetDecimal128 = FunctionDictGet<DataTypeDecimal<Decimal128>, NameDictGetDecimal128>;
using FunctionDictGetString = FunctionDictGet<DataTypeString, NameDictGetString>;
template<typename DataType, typename Name>
using FunctionDictGetOrDefault = FunctionDictGetImpl<DataType, Name, DictionaryGetFunctionType::getOrDefault>;
struct NameDictGetUInt8OrDefault { static constexpr auto name = "dictGetUInt8OrDefault"; };
struct NameDictGetUInt16OrDefault { static constexpr auto name = "dictGetUInt16OrDefault"; };
struct NameDictGetUInt32OrDefault { static constexpr auto name = "dictGetUInt32OrDefault"; };
struct NameDictGetUInt64OrDefault { static constexpr auto name = "dictGetUInt64OrDefault"; };
struct NameDictGetInt8OrDefault { static constexpr auto name = "dictGetInt8OrDefault"; };