Fix mega bug in grade submission

app.py

@@ -124,7 +124,7 @@ def push_results_to_hub(user_answers, token: gr.OAuthToken | None):
     repo_id = f"{EXAM_DATASET_ID}_student_responses"
     submission_time = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
 
-    new_ds = Dataset.from_list([row["is_correct"] for row in user_answers])
+    new_ds = Dataset.from_list([{"is_correct":row["is_correct"]} for row in user_answers])
     new_ds = new_ds.map(
         lambda x: {
             "username": user_info["name"],