Wrong adds a callback fn in an action hook

wp-search-suggest.php: 86

You pass a callback-function name as 'ajax_response' instead 'wpss_ajax_response' for unauthorizated users ??

add_action( 'wp_ajax_nopriv_wp-search-suggest', 'ajax_response' );

Correct:

add_action( 'wp_ajax_nopriv_wp-search-suggest', 'wpss_ajax_response' );