Fixed various PHP 8.2 related warnings.

install/tpl/system.ini.master

server/lib/classes/system.inc.php

server/plugins-available/apache2_plugin.inc.php

server/plugins-available/cron_jailkit_plugin.inc.php

server/plugins-available/cron_plugin.inc.php

server/plugins-available/mail_plugin.inc.php

server/plugins-available/maildeliver_plugin.inc.php

server/plugins-available/nginx_plugin.inc.php

server/plugins-available/postfix_server_plugin.inc.php

server/plugins-available/rspamd_plugin.inc.php

server/plugins-available/shelluser_base_plugin.inc.php

server/plugins-available/shelluser_jailkit_plugin.inc.php

server/plugins-available/webserver_plugin.inc.php