Scenario:
1) Created an application template via application_templates/templates/rails/create.sh
2) Deployed it to my domain via rake descriptors:deploy as railstest
3) Went into the UI, got the following error

NoMethodError (undefined method `git_url=' for nil:NilClass):
  app/models/gear_group.rb:82:in `simplify'
  app/models/application.rb:38:in `gear_groups'
  app/controllers/applications_controller.rb:147:in `show'
  app/models/rest_api/railties/controller_runtime.rb:12:in `process_action'
  lib/streamline/railties/controller_runtime.rb:12:in `process_action'

This is because no cartridges were returned by gear groups

data": [
    {
      "cartridges": [],
      "name": "@@app",
      "gears": [
        {
          "id": "aa99188d57f64b699b88ad7d9d998c95",
          "state": "new"
        }
      ]
    }
  ],

This is either because the descriptor .yaml for the rails example is wrong (and needs to be updated) or because the REST API has bug that needs to be fixed.