Force empty choices to appear

<?php

add_filter( 'facetwp_facet_render_args', function( $args ) {
    if ( 'program_days' == $args['facet']['name'] ) {
        $lookup = [];
        $temp_values = [];
        $days = [ 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday', 'sunday' ];

        foreach ( $args['values'] as $row ) {
            $lookup[ $row['facet_value'] ] = $row;
        }

        foreach ( $days as $day ) {
            if ( isset( $lookup[ $day ] ) ) {
                $temp_values[] = $lookup[ $day ];
            }
            else {
                $temp_values[] = [
                    'facet_value' => $day,
                    'facet_display_value' => ucfirst( $day ),
                    'counter' => 0
                ];
            }
        }

        $args['values'] = $temp_values;
    }

    return $args;
});