fix(frontend): switching accounts never shows the previous account's chats for a moment

frontend/src/lib/stores/chats.svelte.ts

@@ -54,6 +54,9 @@ function createChats() {
   }
 
   function active(): Bucket | undefined {
+    if (account !== accounts.selectedId) {
+      return;
+    }
     return buckets[activeKey()];
   }