Issue: [4.1.0 Alpha 3 Build 004] Preview/Create Post Bug

I created some areas in the wiki
then was going to create and preview a category and when I hit preview I get this error:
Admin - account with full permissions set to yes.

Pressing create new page generates the same error, even if I ignore the category stuff entirely.


Error: Call to a member function set() on null in src/addons/vw/vw/Helper/Entity/Entity.php at line 118
vw\vw\Helper\Entity\Entity::create() in src/addons/vw/vw/_core/model/mention/xf2.php at line 35
vw_Mention_Model_XF2->process() in src/addons/vw/vw/_core/controller/dm/page/vw.php at line 1081
vw_DM_Page_Controller->set_mentions() in src/addons/vw/vw/_core/controller/dm/page/vw.php at line 1015
vw_DM_Page_Controller->process_revision() in src/addons/vw/vw/_core/controller/dm/page/vw.php at line 785
vw_DM_Page_Controller->pre_save() in src/addons/vw/vw/XF/Entity/Entity.php at line 619
vw\vw\XF\Entity\Entity->_preSave() in src/XF/Mvc/Entity/Entity.php at line 1297
XF\Mvc\Entity\Entity->preSave() in src/addons/vw/vw/XF/Entity/Entity.php at line 610
vw\vw\XF\Entity\Entity->vwPreSave() in src/addons/vw/vw/_core/controller/dm/xf2.php at line 329
vw_DM_Controller_XF2->pre_save() in src/addons/vw/vw/_core/controller/ui/edit/page/vw.php at line 494
vw_UI_Edit_Page_Controller->start_dm() in src/addons/vw/vw/_core/controller/ui/edit/page/xf0.php at line 21
vw_UI_Edit_Page_Controller_XF0->start_dm() in src/addons/vw/vw/_core/controller/ui/edit/vw.php at line 149
vw_UI_Edit_Controller->save() in src/addons/vw/vw/_core/controller/ui/create/vw.php at line 431
vw_UI_Create_Controller->publish() in src/addons/vw/vw/_core/controller/ui/area/vw.php at line 145
vw_UI_Area_Controller->publish() in src/addons/vw/vw/_core/controller/ui/area/vw.php at line 47
vw_UI_Area_Controller->execute() in src/addons/vw/vw/_core/controller/ui/stack/vw.php at line 261
vw_UI_Stack_Controller->execute() in src/addons/vw/vw/Pub/Controller/Wiki/Wiki.php at line 80
vw\vw\Pub\Controller\Wiki\Wiki->_actionIndex() in src/addons/vw/vw/Mvc/Dispatcher.php at line 30
vw\vw\Mvc\Dispatcher::dispatch() in src/addons/vw/vw/Pub/Controller/Wiki/AbstractController.php at line 26
vw\vw\Pub\Controller\Wiki\AbstractController->actionIndex() in src/XF/Mvc/Dispatcher.php at line 321
XF\Mvc\Dispatcher->dispatchClass() in src/XF/Mvc/Dispatcher.php at line 248
XF\Mvc\Dispatcher->dispatchFromMatch() in src/XF/Mvc/Dispatcher.php at line 100
XF\Mvc\Dispatcher->dispatchLoop() in src/XF/Mvc/Dispatcher.php at line 50
XF\Mvc\Dispatcher->run() in src/XF/App.php at line 2177
XF\App->run() in src/XF.php at line 390
XF::runApp() in index.php at line 20