title: Can't dup NilClass on rails rake with assets:precompile
body: <p>When I try to precompile my assets I get the following error.  This is the trace with the full output:</p>
  
  <pre><code>RAILS_ENV=production bundle exec rake assets:precompile --trace
  ** Invoke assets:precompile (first_time)
  ** Invoke assets:environment (first_time)
  ** Execute assets:environment
  ** Invoke environment (first_time)
  ** Execute environment
  rake aborted!
  TypeError: can't dup NilClass
  /var/lib/gems/2.3.0/gems/redis-activesupport-5.0.3/lib/active_support/cache/redis_store.rb:38:in `dup'
  /var/lib/gems/2.3.0/gems/redis-activesupport-5.0.3/lib/active_support/cache/redis_store.rb:38:in `map'
  /var/lib/gems/2.3.0/gems/redis-activesupport-5.0.3/lib/active_support/cache/redis_store.rb:38:in `initialize'
  /var/lib/gems/2.3.0/gems/activesupport-5.0.5/lib/active_support/cache.rb:60:in `new'
  /var/lib/gems/2.3.0/gems/activesupport-5.0.5/lib/active_support/cache.rb:60:in `lookup_store'
  /var/lib/gems/2.3.0/gems/railties-5.0.5/lib/rails/application/bootstrap.rb:64:in `block in &lt;module:Bootstrap&gt;'
  /var/lib/gems/2.3.0/gems/railties-5.0.5/lib/rails/initializable.rb:30:in `instance_exec'
  /var/lib/gems/2.3.0/gems/railties-5.0.5/lib/rails/initializable.rb:30:in `run'
  /var/lib/gems/2.3.0/gems/railties-5.0.5/lib/rails/initializable.rb:55:in `block in run_initializers'
  /usr/lib/ruby/2.3.0/tsort.rb:228:in `block in tsort_each'
  /usr/lib/ruby/2.3.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
  /usr/lib/ruby/2.3.0/tsort.rb:431:in `each_strongly_connected_component_from'
  /usr/lib/ruby/2.3.0/tsort.rb:349:in `block in each_strongly_connected_component'
  /usr/lib/ruby/2.3.0/tsort.rb:347:in `each'
  /usr/lib/ruby/2.3.0/tsort.rb:347:in `call'
  /usr/lib/ruby/2.3.0/tsort.rb:347:in `each_strongly_connected_component'
  /usr/lib/ruby/2.3.0/tsort.rb:226:in `tsort_each'
  /usr/lib/ruby/2.3.0/tsort.rb:205:in `tsort_each'
  /var/lib/gems/2.3.0/gems/railties-5.0.5/lib/rails/initializable.rb:54:in `run_initializers'
  /var/lib/gems/2.3.0/gems/railties-5.0.5/lib/rails/application.rb:352:in `initialize!'
  /home/alex/Dev/livingrecipe/config/environment.rb:5:in `&lt;top (required)&gt;'
  /var/lib/gems/2.3.0/gems/activesupport-5.0.5/lib/active_support/dependencies.rb:293:in `require'
  /var/lib/gems/2.3.0/gems/activesupport-5.0.5/lib/active_support/dependencies.rb:293:in `block in require'
  /var/lib/gems/2.3.0/gems/activesupport-5.0.5/lib/active_support/dependencies.rb:259:in `load_dependency'
  /var/lib/gems/2.3.0/gems/activesupport-5.0.5/lib/active_support/dependencies.rb:293:in `require'
  /var/lib/gems/2.3.0/gems/railties-5.0.5/lib/rails/application.rb:328:in `require_environment!'
  /var/lib/gems/2.3.0/gems/railties-5.0.5/lib/rails/application.rb:448:in `block in run_tasks_blocks'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `block in execute'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `each'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `execute'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:194:in `block in invoke_with_call_chain'
  /usr/lib/ruby/2.3.0/monitor.rb:214:in `mon_synchronize'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:187:in `invoke_with_call_chain'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:180:in `invoke'
  /var/lib/gems/2.3.0/gems/sprockets-rails-3.2.0/lib/sprockets/rails/task.rb:62:in `block (2 levels) in define'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `block in execute'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `each'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `execute'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:194:in `block in invoke_with_call_chain'
  /usr/lib/ruby/2.3.0/monitor.rb:214:in `mon_synchronize'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:187:in `invoke_with_call_chain'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:216:in `block in invoke_prerequisites'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:214:in `each'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:214:in `invoke_prerequisites'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:193:in `block in invoke_with_call_chain'
  /usr/lib/ruby/2.3.0/monitor.rb:214:in `mon_synchronize'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:187:in `invoke_with_call_chain'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/task.rb:180:in `invoke'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/application.rb:152:in `invoke_task'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/application.rb:108:in `block (2 levels) in top_level'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/application.rb:108:in `each'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/application.rb:108:in `block in top_level'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/application.rb:117:in `run_with_threads'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/application.rb:102:in `top_level'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/application.rb:80:in `block in run'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/application.rb:178:in `standard_exception_handling'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/lib/rake/application.rb:77:in `run'
  /var/lib/gems/2.3.0/gems/rake-12.0.0/exe/rake:27:in `&lt;top (required)&gt;'
  /usr/local/bin/rake:23:in `load'
  /usr/local/bin/rake:23:in `&lt;main&gt;'
  </code></pre>
  
  <p>So unfortunately I can't figure out where the error is pointing to as none of the code is my stuff and mainly the trace consists of code from the default gems.  The one thing that I can see that I have added in there is the bootstrap gem, but the same thing happens even if I take that out.</p>