wp > Search & Filter > empty result redirect

<?php
    /* this is the very beginning of the index.php */

    /*
    * redirect when search & find is empty:
    * problem: under circumstances (querying by many parameters) there is an empty result and instead of the archive.php the index.php opens
    * hacky solution: check for the parameter 'post_types' in the url on index.php and if found, redirect to the specific archive page
    * note: change the post_types var's to yours, change the url slug fitting your slugs
    */
    if(isset($_GET['post_types'])) {
        $var = $_GET['post_types'];
        if($var == 'publication'){
            wp_safe_redirect( ''.get_home_url().'/publication' ); exit;
        }else if ($var == 'project'){
            wp_safe_redirect( ''.get_home_url().'/projects' ); exit;
        }
    }