title: Polymer Element Error by displaying Image inside FabricJS Canvas
body: <p>I'm trying to display an Image on the FabricJS Canvas inside my Polymer Element. By doing this, this error appears:</p>
  
  <pre><code>Uncaught TypeError: Cannot read property '_set' of undefined
  at klass._onObjectAdded (fabric.js:6964)
  at klass.add (fabric.js:260)
  at HTMLElement.ready (convert-section.html:97)
  at HTMLElement._enableProperties (property-accessors.html:531)
  at HTMLElement.connectedCallback (element-mixin.html:630)
  at HTMLElement._attachDom (element-mixin.html:690)
  at HTMLElement._readyClients (element-mixin.html:663)
  at HTMLElement._flushClients (property-effects.html:1518)
  at HTMLElement._propertiesChanged (property-effects.html:1644)
  at HTMLElement._flushProperties (property-accessors.html:549)
  </code></pre>
  
  <p>Is it possible to display an Image on a FabricJs canvas inside my Polymer Element? Or did I made an misstake? I'm new to Polymer and I don't have much experience.</p>
  
  <p>I can display shapes like triangles etc.</p>
  
  <p><strong>Here is my Element:</strong></p>
  
  <pre><code>&lt;link rel="import" href="../../bower_components/polymer/polymer-element.html"&gt;
  &lt;link rel="import" href="my-paper-element-styles.html"&gt;
  
  &lt;dom-module id="convert-section"&gt;
       &lt;template&gt;
      &lt;style include="my-paper-element-styles"&gt;
      &lt;/style&gt;
  
    &lt;canvas  id="convertCanvas" &gt;&lt;/canvas&gt;
  
    &lt;/template&gt;
       &lt;script&gt;
            class ConvertSection extends Polymer.Element {
                 static get is() {
                      return 'convert-section';
                 }
                 static get properties() {
                      return {
                           imageLocationPath: {
                                type: String,
                                notify: true
                           }
                      };
                 }
                 disconnectedCallback() {
                   super.disconnectedCallback();
                   this.imageLocationPath = "";
                 }
                 ready() {
                      super.ready();
                      this.canvas = this.__canvas = new fabric.Canvas(this.$.convertCanvas);
                      var height = window.innerHeight - 48;
                      var width = window.innerWidth - 300;
                      this.canvas.setHeight(height);
                      this.canvas.setWidth(width);
                      var image = fabric.Image.fromURL('img/viper-board.png');
                      this.canvas.add(image);
                 }
  
            }
            window.customElements.define(ConvertSection.is, ConvertSection);
       &lt;/script&gt;
       &lt;script src="../../node_modules/fabric/dist/fabric.js"&gt;&lt;/script&gt;
  &lt;/dom-module&gt;
  </code></pre>