Fix bug.

app/controllers/admin/seminars_controller.rb

@@ -498,6 +498,7 @@ class Admin::SeminarsController < OrbitAdminController
           seminar_submission_values.each do |v|
             if v.seminar_signup_contribute.nil?
               v.destroy
+              next
             end
             next if v.val.to_i.to_s != v.val
             seminar_session = @seminar.seminar_sessions.where(:key=>v.val.to_i).first