add check in case there is a mismatch between users and people

db/migrate/20140610165551_migrate_data_person_to_user.rb

@@ -9,7 +9,8 @@ class MigrateDataPersonToUser < ActiveRecord::Migration
 
   def change
     TempPerson.all.each do |p|
-      user = TempUser.find(p.user_id)
+      user = TempUser.where('id = ?', p.user_id).first
+      unless user.nil?
         if p.public_name.empty?
           user.name = p.email
         else
@@ -25,4 +26,5 @@ class MigrateDataPersonToUser < ActiveRecord::Migration
         user.save!
       end
     end
+  end
 end