Error message on using crontab

Hello, due to performance reasons I’m not using native WordPress Cron, but calling this wp-cron.php from Linux crontab “*/10 * * * * /usr/bin/php /<wordpress-dir>/wp-cron.php“. Unfortunately this causes every 10 minutes an error message Undefined array key "SCRIPT_FILENAME" in /<wordpress-dir>/wp-content/plugins/delete-me/delete-me.php on line 30“, because $_SERVER[‘SCRIPT_FILENAME’] is not set from CLI. I now added “if (isset($_SERVER['SCRIPT_FILENAME']))” before line 30 in the mentioned file. As this is not upgrade safe and will be overwritten with any new version of “Delete Me”, I kindly ask you, if it would be possible to add this line also to the original file.