Fix bug.

app/controllers/admin/seminars_controller.rb

@@ -584,7 +584,7 @@ class Admin::SeminarsController < OrbitAdminController
             end
           end
         else
-          if seminar_main.seminar_sessions.where(:seminar_signup_ids.ne=>[]).count == 0
+          if @seminar.seminar_sessions.where(:seminar_signup_ids.ne=>[]).count == 0
             @seminar.update(:assign_mode => 0)
           else
             @seminar.update(:assign_mode => 1)