Fix bug on new post creation where we would try to hide an element that wasn't there

common/static/common/js/discussion/views/discussion_inline_view.js

@@ -156,9 +156,11 @@
             this.$('.inline-thread').addClass('is-hidden');
 
             // Delete the thread view
+            if (this.threadView) {
                 this.threadView.$el.empty().off();
                 this.threadView.stopListening();
                 this.threadView = null;
+            }
 
             // Show the thread list view
             this.threadListView.$el.removeClass('is-hidden');