BUGFIX: facebook does not always provide username

We key on facebook_user_id its the only thing that matters

app/models/facebook_user_info.rb

@@ -9,7 +9,7 @@ end
 #  id               :integer          not null, primary key
 #  user_id          :integer          not null
 #  facebook_user_id :integer          not null
-#  username         :string(255)      not null
+#  username         :string(255)
 #  first_name       :string(255)
 #  last_name        :string(255)
 #  email            :string(255)
@@ -24,4 +24,3 @@ end
 #  index_facebook_user_infos_on_facebook_user_id  (facebook_user_id) UNIQUE
 #  index_facebook_user_infos_on_user_id           (user_id) UNIQUE
 #
-

db/migrate/20140320042653_facebook_user_infos_username_can_be_nil.rb

@@ -0,0 +1,5 @@
+class FacebookUserInfosUsernameCanBeNil < ActiveRecord::Migration
+  def change
+    change_column "facebook_user_infos", :username, :string, null: true
+  end
+end