title: Core data migration after changing model
body: <p>I have changed my Core Data model a while back and found out after weeks that it causes a crash on older versions of the app. I get the error:</p>
  
  <pre><code>Error Domain=NSCocoaErrorDomain Code=134140 "Persistent store migration failed, missing mapping model." 
  </code></pre>
  
  <p>My issue is that I don't remember changing anything in my model and have no idea what is causing the migration problem. Is there any way for me to find this out, or have a look at the the model from the older version?</p>
  
  <p>(My project was not under version control at this time.)</p>