Unable to find class 'wcf\system\event\listener\VisitorListener'

Mon, 16 Mar 2020 08:01:01 +0000
Message: Unable to find class 'wcf\system\event\listener\VisitorListener'
PHP version: 7.3.11-nmm1
WoltLab Suite version: 5.2.3
Request URI: /calendar/daily/2028/3/4/
Referrer: 
User Agent: Mozilla/5.0 (compatible; AhrefsBot/6.1; +http://ahrefs.com/robot/)
Peak Memory Usage: 14510656/536870912
======
Error Class: wcf\system\exception\SystemException
Error Message: Unable to find class 'wcf\system\event\listener\VisitorListener'
Error Code: 0
File: /www/htdocs/w017d50e/oggersheim-online.de/lib/system/event/EventHandler.class.php (200)
Extra Information: -
Stack Trace: [{"file":"\/www\/htdocs\/w017d50e\/oggersheim-online.de\/lib\/system\/template\/TemplateEngine.class.php","line":338,"function":"fireAction","class":"wcf\\system\\event\\EventHandler","type":"->","args":["wcf\\system\\template\\TemplateEngine","afterDisplay"]},{"file":"\/www\/htdocs\/w017d50e\/oggersheim-online.de\/lib\/page\/AbstractPage.class.php","line":323,"function":"display","class":"wcf\\system\\template\\TemplateEngine","type":"->","args":["daily","calendar"]},{"file":"\/www\/htdocs\/w017d50e\/oggersheim-online.de\/lib\/page\/AbstractPage.class.php","line":114,"function":"show","class":"wcf\\page\\AbstractPage","type":"->","args":[]},{"file":"\/www\/htdocs\/w017d50e\/oggersheim-online.de\/lib\/system\/request\/Request.class.php","line":83,"function":"__run","class":"wcf\\page\\AbstractPage","type":"->","args":[]},{"file":"\/www\/htdocs\/w017d50e\/oggersheim-online.de\/lib\/system\/request\/RequestHandler.class.php","line":107,"function":"execute","class":"wcf\\system\\request\\Request","type":"->","args":[]},{"file":"\/www\/htdocs\/w017d50e\/oggersheim-online.de\/calendar\/index.php","line":9,"function":"handle","class":"wcf\\system\\request\\RequestHandler","type":"->","args":["calendar"]}]