update: Fix default value assignment for existing data in save_reactions_to_dataset function

app.py

@@ -69,7 +69,7 @@ def save_reactions_to_dataset(user_type, username, query, results_mpnet, results
         for key in data:
             if key not in existing_data:
                 # Add default values for existing rows
-                existing_data[key] = ["" if key in ["user_type", "username", "model_type"] else None] * len(existing_data.get(next(iter(existing_data)), []))
+                existing_data[key] = ["" if key in ["username", "model_type"] else None] * len(existing_data.get(next(iter(existing_data)), []))
             existing_data[key].extend(data[key])
     except Exception:
         # If dataset doesn't exist, use the new data structure