500s on Blitline, no add'l data

gistfile1.rb

# This job:
    blitline.add_job_via_hash(
      application_id: ENV['BLITLINE_APP_ID'],
      src:            flickr_url,
      functions: [
        {
          name:      'scale', 
          params:    {'scale_factor' => 1.5},
          functions: [
            {
              name:      'blur',
              params:    {'sigma' => 1.0},
              functions: [
                {
                  name:   'resize_to_fit',
                  params: {'width' => 1600, 'height' => 1200},
                  save:   {
                           'image_identifier' => "#{city_name}_#{Time.now.to_i}",
                           'quality' => 55
                  }
                }
              ]
            }
          ]
        }
      ]
    )

# Returns a "500 Internal Server Error" with the following headers:
{
   "response":{
      "cache-control":[
         "no-cache"
      ],
      "content-type":[
         "application/json; charset=utf-8"
      ],
      "date":[
         "Sat, 08 Dec 2012 19:06:29 GMT"
      ],
      "server":[
         "nginx/1.0.5"
      ],
      "set-cookie":[
         "_blitline_session=BAh7BkkiD3Nlc3Npb25faWQGOgZFRiIlZDBiOTZhM2MyOTkyMjY2MjFmNTg4Zjg5OWNkNGExY2U%3D--8edb5adc354bafa241a4b2113fd80de03b08a708; path=/; HttpOnly"
      ],
      "status":[
         "500 Internal Server Error"
      ],
      "x-runtime":[
         "0.005237"
      ],
      "x-ua-compatible":[
         "IE=Edge,chrome=1"
      ],
      "content-length":[
         "56"
      ],
      "connection":[
         "Close"
      ]
   }
}

# And this body:
{"results":"undefined method `empty?' for nil:NilClass"}