Besucher in Echtzeit ERROR!

Hallo!

Ich weiss einfach nicht was ich mit dieser Meldung Anfangen soll. Sie erscheint bei “Besucher in Echtzeit” , Piwik 1.12:
Notice: Undefined index: config_device_type in /var/www/piwik/plugins/Live/Visitor.php on line 514

Backtrace -->

#0 Piwik_ErrorHandler(…) called at [/var/www/piwik/plugins/Live/Visitor.php:514]
#1 Piwik_Live_Visitor->getDeviceType(…) called at [/var/www/piwik/plugins/Live/Visitor.php:110]
#2 Piwik_Live_Visitor->getAllVisitorDetails(…) called at [/var/www/piwik/plugins/Live/API.php:167]
#3 Piwik_Live_API->getCleanedVisitorsFromDetails(…) called at [/var/www/piwik/plugins/Live/API.php:133]
#4 Piwik_Live_API->getLastVisitsDetails(…) called at [:]
#5 call_user_func_array(…) called at [/var/www/piwik/core/API/Proxy.php:188]
#6 Piwik_API_Proxy->call(…) called at [/var/www/piwik/core/API/Request.php:145]
#7 Piwik_API_Request->process(…) called at [/var/www/piwik/plugins/Live/Controller.php:125]
#8 Piwik_Live_Controller->getLastVisitsStart(…) called at [/var/www/piwik/plugins/Live/Controller.php:30]
#9 Piwik_Live_Controller->widget(…) called at [:]
#10 call_user_func_array(…) called at [/var/www/piwik/core/FrontController.php:125]
#11 Piwik_FrontController->dispatch(…) called at [/var/www/piwik/index.php:47]

Weiss jemand woran es liegt ?

Grüße