FIX: `topic.details` is not a plain JS Object

FIX: topic.details is not a plain JS Object

diff --git a/app/assets/javascripts/discourse/app/models/topic.js b/app/assets/javascripts/discourse/app/models/topic.js
index 98b0669..604fda2 100644
--- a/app/assets/javascripts/discourse/app/models/topic.js
+++ b/app/assets/javascripts/discourse/app/models/topic.js
@@ -554,6 +554,7 @@ const Topic = RestModel.extend({
       }
     }
     keys.forEach(key => this.set(key, json[key]));
+    return this;
   },
 
   reload() {
diff --git a/test/javascripts/components/select-kit/topic-notifications-button-test.js b/test/javascripts/components/select-kit/topic-notifications-button-test.js
index 6f2f286..fd23bdf 100644
--- a/test/javascripts/components/select-kit/topic-notifications-button-test.js
+++ b/test/javascripts/components/select-kit/topic-notifications-button-test.js
@@ -5,7 +5,8 @@ import Topic from "discourse/models/topic";
 
 const buildTopic = function(level, archetype = "regular") {
   return Topic.create({
-    id: 4563,
+    id: 4563
+  }).updateFromJson({
     title: "Qunit Test Topic",
     details: {
       notification_level: level

GitHub sha: 16766a5d