title: Ember.js: Cannot call get with 'isNew' on an undefined object
body: <p>I have a model with findQuery to send REST request to retrieve data from server, but when the data returned, an exception printed in console:</p>
  
  <pre><code>Error: Assertion Failed: Cannot call get with 'isNew' on an undefined object.
      at new Error (native)
      at Error.EmberError (http://localhost:4200/assets/vendor.js:22563:21)
      at Object.Ember.default.assert (http://localhost:4200/assets/vendor.js:15711:13)
      at get (http://localhost:4200/assets/vendor.js:26145:22)
      at null.&lt;anonymous&gt; (http://localhost:4200/assets/vendor.js:68265:14)
      at Descriptor.ComputedPropertyPrototype.get (http://localhost:4200/assets/vendor.js:20906:26)
      at Object.get (http://localhost:4200/assets/vendor.js:26166:19)
      at exports.default.mixin.Mixin.create.get (http://localhost:4200/assets/vendor.js:40899:27)
      at ember$data$lib$system$relationships$state$relationship$$Relationship.flushCanonical (http://localhost:4200/assets/vendor.js:67250:36)
      at Queue.invoke (http://localhost:4200/assets/vendor.js:11420:18)
  </code></pre>
  
  <p>The following shows the call stack:
  <img src="https://i.stack.imgur.com/6wslJ.png" alt="enter image description here"></p>
  
  <p>The code is just OK when I use grunt, with ember-data 1.0 beta 7. Now I use ember-cli with ember-data 1.0 beta 16.</p>
  
  <p>Any advice?</p>
  
  <p>This picture shows the payload:
  <img src="https://i.stack.imgur.com/fA8zC.png" alt="enter image description here"></p>