Fix/empty result

Dear Denis, This is a request to add our changes to main mainly coming from https://gitlab.com/gaia-x/data-infrastructure-federation-services/cat/fc-service/-/issues/107 . From the understanding of your comment on https://gitlab.com/gaia-x/data-infrastructure-federation-services/cat/fc-service/-/issues/107#note_1180389177 , we have decided to filter null records as a whole. Also we added a test for some clarity. With this new method, it removes all null records from result set. We will ofcourse follow your threads and resolve it soonest.

Best Regards Nikhil Acharya