Use HTMLBars API for inserting partials and views

app/assets/javascripts/admin/templates/user_index.hbs

@@ -316,7 +316,7 @@
     </div>
   {{/if}}
 
-  <div class='display-row' {{bind-attr class=":display-row blocked:highlight-danger"}}>
+  <div {{bind-attr class=":display-row blocked:highlight-danger"}}>
     <div class='field'>{{i18n 'admin.user.blocked'}}</div>
     <div class='value'>{{blocked}}</div>
     <div class='controls'>

app/assets/javascripts/discourse/helpers/custom-html.js.es6

@@ -1,9 +1,11 @@
-Ember.Handlebars.registerHelper('custom-html', function(name, contextString, options) {
-  var html = Discourse.HTML.getCustomHTML(name);
+Ember.HTMLBars._registerHelper('custom-html', function(params, hash, options, env) {
+  const name = params[0];
+  const html = Discourse.HTML.getCustomHTML(name);
   if (html) { return html; }
 
-  var container = (options || contextString).data.view.container;
+  const contextString = params[1];
+  const container = (env || contextString).data.view.container;
   if (container.lookup('template:' + name)) {
-    return Ember.Handlebars.helpers.partial.apply(this, arguments);
+    return env.helpers.partial.helperFunction.apply(this, arguments);
   }
 });

app/assets/javascripts/discourse/helpers/plugin-outlet.js.es6

@@ -123,16 +123,5 @@ Ember.HTMLBars._registerHelper('plugin-outlet', function(params, hash, options,
         });
       }
     }
-  } else if (options.fn) {
-    // If a block is passed, render its content.
-    return Ember.Handlebars.helpers.view.call(this,
-              [Ember.View.extend({
-                isVirtual: true,
-                tagName: '',
-                template: function() {
-                  return options.hash.template;
-                }.property()
-              })],
-            hash, options, env);
   }
 });