解決Ruby升級後發生的has_many NoMethodError: undefined method `name' for nil:NilClass問題

rvm 2.1.4跑起來正常的專案，升級rvm 2.2.2就噴下面錯誤訊息要怎麼修正它呢？
https://github.com/shawnkaku/postit-solution.git
補充：下載後要先bundle update json sqlite3

感謝網友蔡鴻銘指導

https://github.com/....../active_scaffold/issues/380......
升級到rails 4.1.16 + ruby 2.2.4 問題就消失了

Step 1:安裝rvm 2.2.4
$ rvm install 2.2.4
$ rvm use 2.2.4
Using /Users/shawnkuo/.rvm/gems/ruby-2.2.4

Step 2: 修改Gemfile

source 'https://rubygems.org'
ruby '2.2.4'
gem 'rails', '4.1.16'

Step 3:升級專案套件

$ ruby -v
ruby 2.2.4p230 (2015-12-16 revision 53155) [x86_64-darwin17]
$ bundle install
Fetching gem metadata from https://rubygems.org/..........
Fetching gem metadata from https://rubygems.org/.
Resolving dependencies...
Bundler could not find compatible versions for gem "activesupport":
  In snapshot (Gemfile.lock):
    activesupport (= 4.0.0)

  In Gemfile:
    sass-rails (~> 4.0.0) was resolved to 4.0.0, which depends on
      sprockets-rails (~> 2.0.0) was resolved to 2.0.0, which depends on
        actionpack (>= 3.0) was resolved to 4.0.0, which depends on
          activesupport (= 4.0.0)

    rails (= 4.1.16) was resolved to 4.1.16, which depends on
      activesupport (= 4.1.16)

Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.
$ bundle update


Step 4:完成

$ rails s