only execude code when backbone is defined

lms/static/coffee/src/discussion/discussion_module.coffee

-class @DiscussionModuleView extends Backbone.View
-  events:
-    "click .discussion-show": "toggleDiscussion"
-  toggleDiscussion: (event) ->
-    if @showed
-      @$("section.discussion").hide()
-      $(event.target).html("Show Discussion")
-      @showed = false
-    else
-      if @retrieved
-        @$("section.discussion").show()
-        $(event.target).html("Hide Discussion")
-        @showed = true
+if Backbone?
+  class @DiscussionModuleView extends Backbone.View
+    events:
+      "click .discussion-show": "toggleDiscussion"
+    toggleDiscussion: (event) ->
+      if @showed
+        @$("section.discussion").hide()
+        $(event.target).html("Show Discussion")
+        @showed = false
       else
-        $elem = $(event.target)
-        discussion_id = $elem.attr("discussion_id")
-        url = DiscussionUtil.urlFor 'retrieve_discussion', discussion_id
-        Discussion.safeAjax
-          $elem: $elem
-          url: url
-          type: "GET"
-          dataType: 'json'
-          success: (response, textStatus) =>
-            @$el.append(response.html)
-            $discussion = @$el.find("section.discussion")
-            $(event.target).html("Hide Discussion")
-            discussion = new Discussion()
-            discussion.reset(response.discussionData, {silent: false})
-            view = new DiscussionView(el: $discussion[0], model: discussion)
-            DiscussionUtil.bulkUpdateContentInfo(window.$$annotated_content_info)
-            @retrieved = true
-            @showed = true
+        if @retrieved
+          @$("section.discussion").show()
+          $(event.target).html("Hide Discussion")
+          @showed = true
+        else
+          $elem = $(event.target)
+          discussion_id = $elem.attr("discussion_id")
+          url = DiscussionUtil.urlFor 'retrieve_discussion', discussion_id
+          Discussion.safeAjax
+            $elem: $elem
+            url: url
+            type: "GET"
+            dataType: 'json'
+            success: (response, textStatus) =>
+              @$el.append(response.html)
+              $discussion = @$el.find("section.discussion")
+              $(event.target).html("Hide Discussion")
+              discussion = new Discussion()
+              discussion.reset(response.discussionData, {silent: false})
+              view = new DiscussionView(el: $discussion[0], model: discussion)
+              DiscussionUtil.bulkUpdateContentInfo(window.$$annotated_content_info)
+              @retrieved = true
+              @showed = true

lms/static/coffee/src/discussion/main.coffee

@@ -12,4 +12,5 @@ $ ->
     discussion.reset(discussionData, {silent: false})
     view = new DiscussionView(el: elem, model: discussion)
 
-  DiscussionUtil.bulkUpdateContentInfo(window.$$annotated_content_info)
+  if window.$$annotated_content_info?
+    DiscussionUtil.bulkUpdateContentInfo(window.$$annotated_content_info)