Update app.py

app.py

@@ -413,7 +413,7 @@ def identify_headers_and_save_excel(pdf_path, model, llm_prompt):
     result = identify_headers_with_openrouter(pdf_path, model, llm_prompt)
     
     if not result:
-    
+        return None
     df = pd.DataFrame(result)
     
     # Save Excel to a file on disk