Filtering status column in task overview throws error

Problem: Using a filter on the task overviews status column throws an error.

Trace:
ZfExtended_Log on www.translate5.net: Undefined property: stdClass::$property; File: /webs/www.translate5.net/library/ZfExtended/Models/Filter/ExtJs5.php; Line: 78; errno: 8
current user: manager

#0 /webs/www.translate5.net/library/ZfExtended/Models/Filter/ExtJs5.php(78): ZfExtended_Resource_ErrorHandler::errorHandler(8, 'Undefined prope...', '/webs/www.trans...', 78, Array)
#1 /webs/www.translate5.net/library/ZfExtended/Models/Filter/ExtJs5.php(62): ZfExtended_Models_Filter_ExtJs5->convert(Object(stdClass))
#2 /webs/www.translate5.net/library/ZfExtended/Models/Filter.php(91): ZfExtended_Models_Filter_ExtJs5->decode(Array)
#3 [internal function]: ZfExtended_Models_Filter->__construct(Object(editor_Models_Task), Array)
#4 /webs/www.translate5.net/library/ZfExtended/Factory.php(56): ReflectionClass->newInstanceArgs(Array)
#5 /webs/www.translate5.net/library/ZfExtended/Models/Filter/ExtJs.php(141): ZfExtended_Factory::get('editor_Models_F...', Array)
#6 /webs/www.translate5.net/library/ZfExtended/Models/Filter/ExtJs.php(102): ZfExtended_Models_Filter_ExtJs->applyExpression(Object(stdClass), true)
#7 /webs/www.translate5.net/library/ZfExtended/Models/Filter.php(194): ZfExtended_Models_Filter_ExtJs->checkAndApplyOneFilter(Object(stdClass))
#8 /webs/www.translate5.net/application/modules/editor/Models/Task.php(170): ZfExtended_Models_Filter->applyToSelect(Object(Zend_Db_Table_Select), false)
#9 /webs/www.translate5.net/application/modules/editor/Controllers/TaskController.php(169): editor_Models_Task->getTotalCountByUserAssoc('{e6828cdf-2ee0-...', true)
#10 /webs/www.translate5.net/application/modules/editor/Controllers/TaskController.php(149): editor_TaskController->loadAll()
#11 /webs/includes/ZendFramework-1.12.9-minimal/library/Zend/Controller/Action.php(516): editor_TaskController->indexAction()
#12 /webs/www.translate5.net/library/ZfExtended/Controllers/AAARestController.php(234): Zend_Controller_Action->dispatch('indexAction')
#13 /webs/includes/ZendFramework-1.12.9-minimal/library/Zend/Controller/Dispatcher/Standard.php(308): ZfExtended_RestController->dispatch('indexAction')
#14 /webs/includes/ZendFramework-1.12.9-minimal/library/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(REST_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#15 /webs/includes/ZendFramework-1.12.9-minimal/library/Zend/Application/Bootstrap/Bootstrap.php(101): Zend_Controller_Front->dispatch()
#16 /webs/includes/ZendFramework-1.12.9-minimal/library/Zend/Application.php(366): Zend_Application_Bootstrap_Bootstrap->run()
#17 /webs/www.translate5.net/library/ZfExtended/BaseIndex.php(157): Zend_Application->run()
#18 /webs/www.translate5.net/public/index.php(43): ZfExtended_BaseIndex->startApplication()
#19

{main}

Aufgerufene URL inkl. ggf. vorhandener POST-Parameter als get-Parameter:

/editor/task/index/_dc/1474033487176/page/1/start/0/limit/20/filter/[

{"operator":"in","value":["user_state_open","user_state_waiting"],"property":"state"}

]/format/json