error msg after upgrade (no replies)

Hi, I recieved the following error message in "visitors in real-time" / "visitor log"
Things 'seems' to be are still in function... not sure what is wrong
can someone please help?

Notice: Undefined index: visitor_log_maximum_actions_per_visit in /var/www/vhosts/in-mommy.com/httpdocs/piwik/plugins/Live/API.php on line 157

Backtrace -->

#0 Piwik_ErrorHandler(...) called at [/var/www/vhosts/in-mommy.com/httpdocs/piwik/plugins/Live/API.php:157]
#1 Piwik_Live_API->getCleanedVisitorsFromDetails(...) called at [/var/www/vhosts/in-mommy.com/httpdocs/piwik/plugins/Live/API.php:133]
#2 Piwik_Live_API->getLastVisitsDetails(...) called at [:]
#3 call_user_func_array(...) called at [/var/www/vhosts/in-mommy.com/httpdocs/piwik/core/API/Proxy.php:188]
#4 Piwik_API_Proxy->call(...) called at [/var/www/vhosts/in-mommy.com/httpdocs/piwik/core/API/Request.php:145]
#5 Piwik_API_Request->process(...) called at [/var/www/vhosts/in-mommy.com/httpdocs/piwik/plugins/Live/Controller.php:125]
#6 Piwik_Live_Controller->getLastVisitsStart(...) called at [/var/www/vhosts/in-mommy.com/httpdocs/piwik/plugins/Live/Controller.php:30]
#7 Piwik_Live_Controller->widget(...) called at [:]
#8 call_user_func_array(...) called at [/var/www/vhosts/in-mommy.com/httpdocs/piwik/core/FrontController.php:125]
#9 Piwik_FrontController->dispatch(...) called at [/var/www/vhosts/in-mommy.com/httpdocs/piwik/index.php:47]