If only the "app" and "dataset_name" parameters are given, at the first loading of the FilterWidget:
1. Try to load the custom filter (person_id = logged user person_id) with the given "app" and "dataset_name" that is set as default filter (default_filter = true)
2. Try to load the global filter (person_id = null) with the given "app" and "dataset_name" that is set as default filter (default_filter = true)
3. Do not load anything to avoid to retrive too many data from DB