Set initial data to null

Author: DarrenN

app/components/chartist-chart.js

@@ -44,6 +44,7 @@ export default Ember.Component.extend({
     return this.get('type').capitalize();
   }.property('type'),
 
+  data: null,
   options: UNDEF,
   responsiveOptions: UNDEF,
   updateOnData: true,