Fixup change:active_at handling when setting null

When a conversation goes from active to not active, it should be removed
the view rather than promoted.

// FREEBIE

js/views/conversation_list_view.js

@@ -8,10 +8,14 @@
     Whisper.ConversationListView = Whisper.ListView.extend({
         tagName: 'div',
         itemView: Whisper.ConversationListItemView,
-        moveToTop: function(conversation) {
+        onChangeActiveAt: function(conversation) {
             var $el = this.$('.' + conversation.cid);
             if ($el && $el.length > 0) {
-                $el.prependTo(this.el);
+                if (conversation.get('active_at')) {
+                    $el.prependTo(this.el);
+                } else {
+                    $el.remove();
+                }
             }
         }
     });

js/views/inbox_view.js

@@ -87,17 +87,17 @@
                     this.openConversation.bind(this, null));
 
                 var inboxCollection = bg.getInboxCollection();
-                this.inboxView = new Whisper.ConversationListView({
+                this.inboxListView = new Whisper.ConversationListView({
                     el         : this.$('.conversations'),
                     collection : inboxCollection
                 }).render();
 
-                this.inboxView.listenTo(inboxCollection, 'change:active_at', this.inboxView.moveToTop);
+                this.inboxListView.listenTo(inboxCollection, 'change:active_at', this.inboxListView.onChangeActiveAt);
 
                 new SocketView().render().$el.appendTo(this.$('.socket-status'));
 
                 extension.windows.beforeUnload(function() {
-                    this.inboxView.stopListening();
+                    this.inboxListView.stopListening();
                 }.bind(this));
 
                 new Whisper.WindowControlsView({