diff --git a/src/utils/time.ts b/src/utils/time.ts
index c89c1cd..a3bb0bf 100644
--- a/src/utils/time.ts
+++ b/src/utils/time.ts
@@ -43,14 +43,15 @@ export function formatTimestamp(timestamp: number): string {
         // Both have timestamp, sort by timestamp descending
         return b.timestamp - a.timestamp;
       } else if (a.timestamp) {
-        // Only `a` has timestamp, it comes first
         return -1;
       } else if (b.timestamp) {
-        // Only `b` has timestamp, it comes first
         return 1;
       } else {
-        // Neither has timestamp, sort alphabetically by groupName
-        return a.groupName.localeCompare(b.groupName);
+        // Neither has timestamp, sort alphabetically by groupName (with fallback)
+        const nameA = a.groupName || '';
+        const nameB = b.groupName || '';
+        return nameA.localeCompare(nameB);
       }
     });
-  }
\ No newline at end of file
+  }
+  
\ No newline at end of file