argument error in theme (with code)

Hi, To display random results within my theme I am getting an error saying that the second argument is missing. Can you tell me what is wrong with this code that I've placed in my functions.php file?
This is the error:
Warning: Missing argument 2 for custom_orderby() in /home/user/public_html/path/wp-content/themes/listify-child/functions.php on line 12

This is the code:

function custom_orderby( $query_args, $args ) {
    $args[ 'orderby' ] = 'rand';

    return $args;
add_filter( 'get_job_listings_query_args', 'custom_orderby', 99 );