**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:`

{
    using Type = typename DataType::FieldType;
public:
    static constexpr auto name = Name::name;
    static FunctionPtr create(const Context &context)
    {
        return std::make_shared<FunctionDictGetImpl>(context);
    }
    explicit FunctionDictGetImpl(const Context & context_) : impl(context_) {}
    String getName() const override { return name; }
private:
    size_t getNumberOfArguments() const override { return 0; }
    bool isVariadic() const override { return true; }
    bool useDefaultImplementationForConstants() const final { return true; }
    bool isDeterministic() const override { return false; }
    ColumnNumbers getArgumentsThatAreAlwaysConstant() const final { return {0, 1}; }
    bool isInjective(const ColumnsWithTypeAndName & sample_columns) const override
    {
        return impl.isInjective(sample_columns);
    }
    DataTypePtr getReturnTypeImpl(const DataTypes &) const override
    {
        DataTypePtr result;
        if constexpr (IsDataTypeDecimal<DataType>)
            result = std::make_shared<DataType>(DataType::maxPrecision(), 0);
        else
            result = std::make_shared<DataType>();
        return result;
    }
    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr & result_type, size_t input_rows_count) const override