7.x deprecated: SearchApiElasticsearchBackend::deleteItems(): Implicitly marking parameter $index as nullable

Problem/Motivation

Getting this error on the latest 7.x commit with PHP 8.4:

PHP Deprecated: Drupal\elasticsearch_connector\Plugin\search_api\backend\SearchApiElasticsearchBackend::deleteItems(): Implicitly marking parameter $index as nullable is deprecated, the explicit nullable type must be used instead in /var/www/html/bonjourquebec/web/modules/contrib/elasticsearch_connector/src/Plugin/search_api/backend/SearchApiElasticsearchBackend.php on line 534