title: Asset precompilation fails after rails upgrade
body: <p>I just upgraded from Rails 4.0.4 to 4.1.8, and when I push to our staging server on Heroku, I get the following error</p>
  
  <pre><code>Removing jquery-rails (3.0.4)
  -----&gt; Preparing app for Rails asset pipeline
         Running: rake assets:precompile
         rake aborted!
         NoMethodError: undefined method `[]=' for nil:NilClass
         /tmp/build_6e5605f8ccbbe1dcb495bb63b761220d/config/initializers/puma_database_connection.rb:7:in `block (2 levels) in &lt;top (required)&gt;'
         /tmp/build_6e5605f8ccbbe1dcb495bb63b761220d/vendor/bundle/ruby/2.0.0/gems/activesupport-4.1.8/lib/active_support/lazy_load_hooks.rb:38:in `instance_eval'
         /tmp/build_6e5605f8ccbbe1dcb495bb63b761220d/vendor/bundle/ruby/2.0.0/gems/activesupport
         /tmp/build_6e5605f8ccbbe1dcb495bb63b761220d/vendor/bundle/ruby/2.0.0/gems/railties-
         Tasks: TOP =&gt; environment
         (See full trace by running task with --trace)
   !
   !     Precompiling assets failed.
  </code></pre>
  
  <p>When I run assets:precompile RAILS_ENV=development, it works fine</p>
  
  <p>Any advice?</p>