Add records that indicate a user's avatar has been checked

db/migrate/20130912185218_acting_user_null.rb

@@ -0,0 +1,10 @@
+class ActingUserNull < ActiveRecord::Migration
+  def up
+    change_column :user_histories, :acting_user_id, :integer, :null => true
+  end
+
+  def down
+    execute "DELETE FROM user_histories WHERE acting_user_id IS NULL"
+    change_column :user_histories, :acting_user_id, :integer, :null => false
+  end
+end