Fatal error: PHP warning in file /var/www/web25/html/wbblite/wcf/lib/system/event/EventHandler.class.php (73): get_class() expects parameter 1 to be object, string given

Information:

error message: PHP warning in file /var/www/web25/html/wbblite/wcf/lib/system/event/EventHandler.class.php (73): get_class() expects parameter 1 to be object, string given
error code: 0
file: /var/www/web25/html/wbblite/wcf/lib/system/WCF.class.php (255)
php version: 5.3.3-7+squeeze27
wcf version: 1.0.10 (Horizon)
date: Wed, 24 Aug 2016 11:58:15 +0000
request: /wbblite/
referer:

Stacktrace:

#0 [internal function]: WCF::handleError(2, 'get_class() exp...', '/var/www/web25/...', 73, Array)
#1 /var/www/web25/html/wbblite/wcf/lib/system/event/EventHandler.class.php(73): get_class('UserAuth')
#2 /var/www/web25/html/wbblite/wcf/lib/system/event/EventHandler.class.php(142): EventHandler::executeInheritedActions('UserAuth', 'loadInstance', 'UserAuth', 'loadInstance@Us...')
#3 /var/www/web25/html/wbblite/wcf/lib/system/auth/UserAuth.class.php(28): EventHandler::fireAction('UserAuth', 'loadInstance')
#4 /var/www/web25/html/wbblite/wcf/lib/system/session/CookieSessionFactory.class.php(34): UserAuth::getInstance()
#5 /var/www/web25/html/wbblite/wcf/lib/system/session/SessionFactory.class.php(71): CookieSessionFactory->create()
#6 /var/www/web25/html/wbblite/lib/system/WBBCore.class.php(170): SessionFactory->get()
#7 /var/www/web25/html/wbblite/wcf/lib/system/WCF.class.php(91): WBBCore->initSession()
#8 /var/www/web25/html/wbblite/global.php(18): WCF->__construct()
#9 /var/www/web25/html/wbblite/index.php(7): require_once('/var/www/web25/...')
#10 {main}