Merge branch '6821-fix-issue-with-operator-in-php-8-3-in-100-mailbox_stats_hourly-inc-php' into 'develop'

Resolve "Fix issue with ?? operator in PHP 8.3 in 100-mailbox_stats_hourly.inc.php"

Closes #6821

See merge request ispconfig/ispconfig3!1974

Author: Till Brehm

server/lib/classes/cron.d/100-mailbox_stats_hourly.inc.php

@@ -96,7 +96,7 @@ private function update_last_mail_login() {
 			$matches = [];
 			// Match pop3/imap logings, or alternately smtp logins.
 			if (preg_match('/(.*) (imap|pop3)-login: Login: user=\<([\w\.@-]+)\>/', $line, $matches) || preg_match('/(.*) sasl_method=PLAIN, sasl_username=([\w\.@-]+)/', $line, $matches)) {
-				$user = $matches[3] ?? $matches[2];
+				$user = isset($matches[3]) ? $matches[3] : $matches[2];
 				$updatedUsers[] = $user;
 			}