Hello IFS Community.

I created a Navigation Link in Page Designer from Product Structure to Inventory Parts in Stock, which takes two parameters, Contract and Part Number.

This is the NavigateFilter, Contract eq $$Contract]

This works as long as the current page has a value in search for Site/Contact. If it does not have a value, the navigation to IPIS will open up with the default Site parameter for the user. 

How can I introduce a filter in that Navigation Link that somehow says if the Site parameter is Null, then pass the same Null value to the destination page. The object is to display all inventory for all Sites/Contracts for that Part Number, or if present, just for that site.