Profile: wabw media group

Problem:
The user would like to hide the results of the view when the filter is empty(no option is selected).
The user is filtering a one-to-many relationship.

Solution:
This needs custom code that will check the filter, and if no value is given, the results are emptied.
Check this reference code:

if ( $view_id === 694 ) { // the view_id
        if ( isset( $_GET['wpv-relationship-filter'] ) && ( $_GET['wpv-relationship-filter'] == 0 ) ) {
            // When no option is selected, the filter will hold 0
            $query_results->posts = array();
            $query_results->post_count = 0;
            $query_results->found_posts = 0;
        }
    }

Notice: This is for an example with one parent-child relationship. Depending on your use case, it may need to be adapted

Relevant Documentation:
https://toolset.com/documentation/programmer-reference/views-filters/#wpv_filter_query_post_process