Fatal error: PHP error in file /www/htdocs/v141994/wbb3/lib/system/event/listener/RGalleryUserPageListener.class.php (20): Non-static method RGallerySystem::getUserItemsListing() should not be called statically, assuming $this from incompatible context

Information:

error message: PHP error in file /www/htdocs/v141994/wbb3/lib/system/event/listener/RGalleryUserPageListener.class.php (20): Non-static method RGallerySystem::getUserItemsListing() should not be called statically, assuming $this from incompatible context
error code: 0
file: /www/htdocs/v141994/wbb3/wcf/lib/system/WCF.class.php (255)
php version: 5.5.38-nmm2
wcf version: 1.0.11 pl 3 (Horizon)
date: Tue, 18 Dec 2018 13:58:01 +0000
request: /wbb3/index.php?page=User&userID=746&s=6cbf8318c9e9ba9ae8f1e90c48b909db9eca4e03
referer:

Stacktrace:

#0 /www/htdocs/v141994/wbb3/lib/system/event/listener/RGalleryUserPageListener.class.php(20): WCF::handleError(2048, 'Non-static meth...', '/www/htdocs/v14...', 20, Array)
#1 /www/htdocs/v141994/wbb3/wcf/lib/system/event/EventHandler.class.php(193): RGalleryUserPageListener->execute(Object(UserPage), 'UserPage', 'assignVariables')
#2 /www/htdocs/v141994/wbb3/wcf/lib/page/AbstractPage.class.php(63): EventHandler::fireAction(Object(UserPage), 'assignVariables')
#3 /www/htdocs/v141994/wbb3/wcf/lib/page/UserPage.class.php(105): AbstractPage->assignVariables()
#4 /www/htdocs/v141994/wbb3/wcf/lib/page/AbstractPage.class.php(77): UserPage->assignVariables()
#5 /www/htdocs/v141994/wbb3/wcf/lib/page/UserPage.class.php(170): AbstractPage->show()
#6 /www/htdocs/v141994/wbb3/wcf/lib/page/AbstractPage.class.php(36): UserPage->show()
#7 /www/htdocs/v141994/wbb3/wcf/lib/page/UserPage.class.php(37): AbstractPage->__construct()
#8 /www/htdocs/v141994/wbb3/wcf/lib/util/RequestHandler.class.php(63): UserPage->__construct()
#9 /www/htdocs/v141994/wbb3/wcf/lib/util/RequestHandler.class.php(91): RequestHandler->__construct('User', Array, 'page')
#10 /www/htdocs/v141994/wbb3/index.php(8): RequestHandler::handle(Array)
#11 {main}