Fix bug.

app/models/seminar_main.rb

@@ -88,7 +88,7 @@ class SeminarMain
       end
     end
     remove_module_app_member_ids.delete(self.organizer_id)
-    self.reviewer_ids.each{|r| remove_module_app_member_ids.delete(r)}
+    self.reviewer_ids.each{|r| remove_module_app_member_ids.delete(r)} rescue nil
     remove_module_app_member_ids.each do |m_id|
       user = User.where(:member_profile_id=>m_id).first
       begin