Error after update to 2.2.0 (no replies)

After updating to Piwik 2.2.0 I get the following message on every page. Everthing seems to work normally. But the large yellow box doesn't look nice.

Quote
There is an error. Please report the message (Piwik 2.2.0) and full backtrace in the Piwik forums (please do a Search first as it might have been reported already!).

Notice: Undefined index: datatable_export_range_as_day in /www/htdocs/w00f0189/html/piwik/core/Config.php on line 228

Backtrace -->

#0 Piwik\Error::errorHandler(...) called at [/www/htdocs/w00f0189/html/piwik/core/Config.php:228]
#1 Piwik\Config->getClientSideOptions(...) called at [/www/htdocs/w00f0189/html/piwik/core/Plugin/Controller.php:550]
#2 Piwik\Plugin\Controller->setBasicVariablesView(...) called at [/www/htdocs/w00f0189/html/piwik/core/Plugin/Controller.php:515]
#3 Piwik\Plugin\Controller->setGeneralVariablesView(...) called at [/www/htdocs/w00f0189/html/piwik/plugins/CoreHome/Controller.php:79]
#4 Piwik\Plugins\CoreHome\Controller->getDefaultIndexView(...) called at [/www/htdocs/w00f0189/html/piwik/plugins/CoreHome/Controller.php:113]
#5 Piwik\Plugins\CoreHome\Controller->index(...) called at [:]
#6 call_user_func_array(...) called at [/www/htdocs/w00f0189/html/piwik/core/FrontController.php:505]
#7 Piwik\FrontController->doDispatch(...) called at [/www/htdocs/w00f0189/html/piwik/core/FrontController.php:85]
#8 Piwik\FrontController->dispatch(...) called at [/www/htdocs/w00f0189/html/piwik/core/dispatch.php:34]
#9 require_once(...) called at [/www/htdocs/w00f0189/html/piwik/index.php:47]

Also the following message only shows up in the Dashboard.

Quote
There is an error. Please report the message (Piwik 2.2.0) and full backtrace in the Piwik forums (please do a Search first as it might have been reported already!).

Notice: Undefined index: datatable_export_range_as_day in /www/htdocs/w00f0189/html/piwik/core/Config.php on line 228

Backtrace -->

#0 Piwik\Error::errorHandler(...) called at [/www/htdocs/w00f0189/html/piwik/core/Config.php:228]
#1 Piwik\Config->getClientSideOptions(...) called at [/www/htdocs/w00f0189/html/piwik/core/Plugin/Controller.php:550]
#2 Piwik\Plugin\Controller->setBasicVariablesView(...) called at [/www/htdocs/w00f0189/html/piwik/core/Plugin/Controller.php:515]
#3 Piwik\Plugin\Controller->setGeneralVariablesView(...) called at [/www/htdocs/w00f0189/html/piwik/plugins/Dashboard/Controller.php:39]
#4 Piwik\Plugins\Dashboard\Controller->_getDashboardView(...) called at [/www/htdocs/w00f0189/html/piwik/plugins/Dashboard/Controller.php:52]
#5 Piwik\Plugins\Dashboard\Controller->embeddedIndex(...) called at [:]
#6 call_user_func_array(...) called at [/www/htdocs/w00f0189/html/piwik/core/FrontController.php:505]
#7 Piwik\FrontController->doDispatch(...) called at [/www/htdocs/w00f0189/html/piwik/core/FrontController.php:85]
#8 Piwik\FrontController->dispatch(...) called at [/www/htdocs/w00f0189/html/piwik/core/dispatch.php:34]
#9 require_once(...) called at [/www/htdocs/w00f0189/html/piwik/index.php:47]

Any idea what could be wrong?