Fix loading newer messages on scroll

ts/models/conversations.ts

@@ -1561,6 +1561,7 @@ export class ConversationModel extends window.Backbone
       });
 
       let messages: ReadonlyArray<MessageAttributesType>;
+      let unboundedFetch = true;
       if (metrics.oldestUnseen) {
         const unseen = await getMessageById(metrics.oldestUnseen.id);
         if (!unseen) {
@@ -1587,6 +1588,7 @@ export class ConversationModel extends window.Backbone
         messages = [...older, unseen, ...newer];
 
         metrics = freshMetrics;
+        unboundedFetch = false;
       } else {
         messages = await getOlderMessagesByConversation({
           conversationId: this.id,
@@ -1607,6 +1609,7 @@ export class ConversationModel extends window.Backbone
         conversationId: this.id,
         messages: cleaned,
         metrics,
+        unboundedFetch,
       });
     } finally {
       finish();

ts/state/ducks/conversations.ts

@@ -439,6 +439,7 @@ export type ConversationPreloadDataType = ReadonlyDeep<{
   conversationId: string;
   messages: ReadonlyArray<ReadonlyMessageAttributesType>;
   metrics: MessageMetricsType;
+  unboundedFetch: boolean;
 }>;
 
 export type MessagesByConversationType = ReadonlyDeep<{
@@ -5672,10 +5673,7 @@ export function reducer(
       return dropPreloadData(state);
     }
 
-    return updateMessageLookup(state, {
+    return updateMessageLookup(state, preloadData);
-      ...preloadData,
-      unboundedFetch: true,
-    });
   }
   if (action.type === 'SET_MESSAGE_LOADING_STATE') {
     const { payload } = action;