Call to a member function getUrl() on bool

(1/1) Error Call to a member function getUrl() on bool
in OnlineShopProductPage.php line 15
at OnlineShopProductPage->getUrl('en')in Controller.php line 37
at Controller->getUrl('en')in PluginController.php(107) : eval()'d code line 123
at eval()in PluginController.php line 107
at PluginController->executeFrontendLayout()in PluginController.php line 85
at PluginController->display('../../plugins/online_shop/views/frontend/product', array('id' => '88'))in OnlineShopController.php line 1217
at OnlineShopController->frontend_product('88')in Controller.php line 153
at Controller->frontend('product', '88')in PluginController.php line 145
at PluginController->execute('frontend', array('product', '88'))in Dispatcher.php line 238
at Dispatcher::executeAction(object(PluginController), 'online_shop', array('frontend', 'product', '88'))in Dispatcher.php line 158
at Dispatcher::dispatch('/shop/product/88/teekanne-glas-soojin')in main.php line 176
at main()in main.php line 235
at require('/home/httpd/vhosts/teelabor.ch/httpdocs/cms/app/main.php')in index.php line 210