Issue: Undefined index: sortkey

ErrorException: Undefined index: sortkey - vault/core/view/content/list/base/vw.php:407
Generated By: Bajeda, 4 minutes ago

Stack Trace
#0 /vault/core/view/content/list/base/vw.php(407): XenForo_Application::handlePhpError(8, 'Undefined index...', '/home/...', 407, Array)
#1 /vault/core/view/content/list/book/vw.php(160): vw_Content_List_Base_View->process_filters(Array, Array, Array)
#2 /vault/core/view/content/list/book/vw.php(47): vw_Content_List_Book_View->query(Array, Array)
#3 /vault/core/view/ui/book/vw.php(344): vw_Content_List_Book_View->get('Page', Array, Array, Array)
#4 /vault/core/controller/ui/book/vw.php(981): vw_UI_Book_View->book_list(Object(vw_UI_Book_Controller))
#5 /vault/core/controller/ui/book/vw.php(65): vw_UI_Book_Controller->book_list()
#6 /vault/core/controller/ui/stack/vw.php(276): vw_UI_Book_Controller->execute()
#7 /library/vw/XenForo/ControllerPublic/Wiki.php(70): vw_UI_Stack_Controller->execute()
#8 /library/XenForo/FrontController.php(351): vw_XenForo_ControllerPublic_Wiki->actionIndex()
#9 /library/XenForo/FrontController.php(134): XenForo_FrontController->dispatch(Object(XenForo_RouteMatch))
#10 /index.php(13): XenForo_FrontController->run()
#11 {main}
Request State
array(3) {
["url"] => string(56) "https://forum.com/wiki/?title=Book:Faq&do=contents"
["_GET"] => array(2) {
["title"] => string(8) "Book:Faq"
["do"] => string(8) "contents"
}
["_POST"] => array(7) {
["filter"] => string(1) "0"
["sort"] => string(5) "title"
["sortorder"] => string(3) "asc"
["_xfToken"] => string(8) "********"
["do"] => string(8) "contents"
["title"] => string(8) "Book:Faq"
["bb2_screener_"] => string(22) "1499786267 xxx"
}
}