Error detail: Invalid value passed to set; please use setMeta()

#0 /home/www/trangdangtin/library/Common/Zend/View/Helper/HeadMeta.php(158): Zend_View_Helper_HeadMeta->set(Object(stdClass))
#1 /home/www/trangdangtin/app/modules/default/controllers/PostsController.php(4906): Zend_View_Helper_HeadMeta->__call('setName', Array)
#2 /home/www/trangdangtin/app/modules/default/controllers/PostsController.php(4906): Zend_View_Helper_HeadMeta->setName('keywords', NULL)
#3 /home/www/trangdangtin/library/Common/Zend/Controller/Action.php(513): Default_PostsController->searchtagsAction()
#4 /home/www/trangdangtin/library/Common/Zend/Controller/Dispatcher/Standard.php(295): Zend_Controller_Action->dispatch('searchtagsActio...')
#5 /home/www/trangdangtin/library/Common/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#6 /home/www/trangdangtin/app/Bootstrap.php(272): Zend_Controller_Front->dispatch()
#7 /home/www/trangdangtin/library/Common/Zend/Application.php(366): Bootstrap->run()
#8 /home/www/trangdangtin/index.php(134): Zend_Application->run()
#9 {main}