navigation on null route parameters ZF2

Question

I wrote a navigation and it works correctly. If I view my page with categoryId 20 then navigator works ok, but I want it also to work if null passed for CategoryId. I show what I expect in comment.

'navigation' => array(

    'default' => array(
        array(
            'label' => 'Home',
            'route' => 'home',
        ),
        array(
            'label' => 'advertiseSearch',
            'route' => 'locate',
            'pages' => array(
                array(
                    'label' => 'advertiseCategorySelect',
                    'route' => 'locate',
                    'params'=>array(
                        'CategoryId'=>'20',// i want 'CategoryId'=>'' or 'CategoryId'=>null
                    )
                )
            ),
        ),
    ),
)

What should I write so that even if CategoryId is not set, the navigator works?

Thank you.