Update app.py

app.py

@@ -182,6 +182,9 @@ def start_labeling(username_label):
 
 
 def show_random_sample(username_label, remaining_batch):
+    if remaining_batch is None or not remaining_batch:
+        raise gr.Error("Make sure you are logged in.")
+    
     rindex = random.choice(remaining_batch)
     remaining_batch.remove(rindex)