bp_search_remove_search_types_for_guests( mixed $search_types )

function bp_search_remove_search_types_for_guests( $search_types ) {
	if ( ! is_admin() && ! empty( $search_types ) && ! is_user_logged_in() ) {
		$items_to_remove       = array( 'messages', 'notifications' );
		$filtered_search_types = array();
		foreach ( $search_types as $search_type ) {
			if ( ! in_array( $search_type, $items_to_remove ) ) {
				$filtered_search_types[] = $search_type;
			}
		}

		$search_types = $filtered_search_types;
	}

	return $search_types;
}