Backtrace -->
#0 Piwik_ErrorHandler(…) called at [/plugins/Forecast/Forecast.php:47]#1 Piwik_Forecast->postLoad(…) called at [/core/PluginsManager.php:267]#2 Piwik_PluginsManager->postLoadPlugins(…) called at [/core/FrontController.php:272]#3 Piwik_FrontController->init(…) called at [/index.php:52]
Maybe disabling the Forecast plugin and contacting the plugin developer.