PHP Warning: max() in sorting.php

The following warning is being thrown if $order returns the empty array:

PHP Warning: max(): Array must contain at least one element in /var/www/html/wp-content/plugins/relevanssi/lib/sorting.php on line 314

Suggestion to resolve would be to set $max_key to zero before line 314 and then only use max($order) if $order is not empty.

$max_key = 0;
// Set the default values so that if the key is not found in the array, it’s last.
if (! empty($order)) $max_key = max( $order );