Declaration of Custom_Menu_Wizard_Walker::walk

From WP 5.3 these warnings appear in the logs:

PHP Warning: Declaration of Custom_Menu_Wizard_Sorter::walk($elements, $max_depth = 0) should be compatible with Walker::walk($elements, $max_depth, …$args) in /wp-content/plugins/custom-menu-wizard/include/class.sorter.php

PHP Warning: Declaration of Custom_Menu_Wizard_Walker::walk($elements, $max_depth) should be compatible with Walker::walk($elements, $max_depth, …$args) in /wp-content/plugins/custom-menu-wizard/include/class.walker.php

Looks like this solves it:
class.walker.php line 55
public function walk( $elements, $max_depth, …$args ){

class.sorter.php line 60
public function walk( $elements, $max_depth = 0, …$args ) {

//NB : any orphan elements (and that includes children of orphans) get appended to the
// output array in the order that they are placed in the original array (ie. regardless
// of menu_order) BUT *only* if $max_depth is zero! If $max_depth is anything other than
// zero then all orphans (and their children) are ignored (ie. discarded).
$output = parent::walk( $elements, $max_depth, …$args );

//always return an array…
return is_array( $output ) ? $output : array();

}