FIX: Use proper iconNode when compiling virtual dom templates

app/assets/javascripts/discourse-common/lib/icon-library.js.es6

@@ -23,6 +23,8 @@ export function iconNode(id, params) {
   return renderIcon('node', id, params);
 }
 
+Discourse.__widget_helpers.iconNode = iconNode;
+
 export function registerIconRenderer(renderer) {
   _renderers.unshift(renderer);
 }

app/assets/javascripts/discourse.js.es6

@@ -7,6 +7,7 @@ const Discourse = Ember.Application.extend({
   rootElement: '#main',
   _docTitle: document.title,
   RAW_TEMPLATES: {},
+  __widget_helpers: {},
 
   getURL(url) {
     if (!url) return url;