title: Fabric js Load canvas from JSON
body: <p>I am trying to implement save and load functions, but I get an error when I'm trying to load the json into the canvas.
  The error message says "Cannot read property 'async' of undefined", but the json output looks good I think. (I'm not used to JavaScript, so I have no idea, if the problem is in fabric or in my code..)</p>
  
  <p>Here is a jsFiddle Link to my test case: <a href="https://jsfiddle.net/f3hkynsu/" rel="noreferrer">Example fiddle</a></p>
  
  <p>The save and load function is like this so far:</p>
  
  <pre><code>var json = JSON.stringify(canvas);
  canvas.clear();
  canvas.loadFromJSON(json, function() {
      canvas.renderAll();
  });       
  </code></pre>
  
  <p>Thanks for your help! :)</p>