Fix bug.

app/controllers/admin/seminars_controller.rb

@@ -55,7 +55,7 @@ class Admin::SeminarsController < OrbitAdminController
         if page
           display_menu << page_id if page.enabled_for.length != 0
         else
-          display_menu << page_id
+          display_menu << page_id if page_id != "registered_participants"
         end
       end
     end