Eliminate some conversation fields which are no longer used

js/models/conversations.js

@@ -128,6 +128,9 @@
       this.unset('unidentifiedDelivery');
       this.unset('unidentifiedDeliveryUnrestricted');
       this.unset('hasFetchedProfile');
+      this.unset('tokens');
+      this.unset('lastMessage');
+      this.unset('lastMessageStatus');
     },
 
     isMe() {
@@ -956,8 +959,8 @@
 
       let hasChanged = false;
       const { lastMessage, lastMessageStatus } = lastMessageUpdate;
-      lastMessageUpdate.lastMessage = null;
-      lastMessageUpdate.lastMessageStatus = null;
+      delete lastMessageUpdate.lastMessage;
+      delete lastMessageUpdate.lastMessageStatus;
 
       hasChanged = hasChanged || lastMessage !== this.lastMessage;
       this.lastMessage = lastMessage;
@@ -1076,7 +1079,7 @@
     },
 
     isSearchable() {
-      return !this.get('left') || !!this.get('lastMessage');
+      return !this.get('left');
     },
 
     async endSession() {

test/views/conversation_search_view_test.js

@@ -65,7 +65,7 @@ describe('ConversationSearchView', function() {
       before(async function() {
         input = $('<input>');
         view = new Whisper.ConversationSearchView({ input: input }).render();
-        convo.set({ id: '2-search-view', lastMessage: 'asdf' });
+        convo.set({ id: '2-search-view', left: false });
 
         await window.Signal.Data.saveConversation(convo.attributes, {
           Conversation: Whisper.Conversation,