A non-numeric value encountered

Got the debug.log filled today with about 40 lines of these:

PHP Warning: A non-numeric value encountered in /wp-content/plugins/advanced-cron-manager/inc/Cron/Element/Event.php on line 92

The code around that line is opaque to me:

public function get_implementation() {

	$arguments = array();
	foreach ( $this->args as $n => $arg ) {
92:		$arguments[] = '$arg' . ( $n + 1 );
	}

Hope you’d find a better way to handle inadequate input for a next version.

Thanks!