Fatal error: PHP error in file /srv/www/vhosts/no-kill.de/httpdocs/lib/page/RGalleryPage.class.php (213): Non-static method RGallerySystem::getCurrentCategorie() should not be called statically, assuming $this from incompatible context

Information:

error message: PHP error in file /srv/www/vhosts/no-kill.de/httpdocs/lib/page/RGalleryPage.class.php (213): Non-static method RGallerySystem::getCurrentCategorie() should not be called statically, assuming $this from incompatible context
error code: 0
file: /srv/www/vhosts/no-kill.de/httpdocs/wcf/lib/system/WCF.class.php (255)
php version: 5.6.36
wcf version: 1.0.11 pl 1 (Horizon)
date: Mon, 16 Jul 2018 18:19:20 +0000
request: /index.php?page=RGallery&rGalleryCat=none&reset_tag=1&s=96c80988478a12d468c01402013a30acad1e30d2
referer:

Stacktrace:

#0 /srv/www/vhosts/no-kill.de/httpdocs/lib/page/RGalleryPage.class.php(213): WCF::handleError(8192, 'Non-static meth...', '/srv/www/vhosts...', 213, Array)
#1 /srv/www/vhosts/no-kill.de/httpdocs/wcf/lib/page/AbstractPage.class.php(36): RGalleryPage->show()
#2 /srv/www/vhosts/no-kill.de/httpdocs/wcf/lib/util/RequestHandler.class.php(63): AbstractPage->__construct()
#3 /srv/www/vhosts/no-kill.de/httpdocs/wcf/lib/util/RequestHandler.class.php(91): RequestHandler->__construct('RGallery', Array, 'page')
#4 /srv/www/vhosts/no-kill.de/httpdocs/index.php(8): RequestHandler::handle(Array)
#5 {main}