Use get for proxy objects at second level #775 to fix broken test

Author: rajakvk

app/components/api-index-filter.js

@@ -90,7 +90,7 @@ export default class ApiIndexFilter extends Component {
    */
   findMostLocal(currentItem, nextItem) {
     let currentScope = this.model.file;
-    let parentClassScope = this.model.get('parentClass').file;
+    let parentClassScope = this.model.get('parentClass').get('file');
     if (currentScope === currentItem.file) {
       // if the item belongs to the class, keep it
       return currentItem;