Update app.py

app.py

@@ -396,6 +396,7 @@ def run_process(file, question, model_choice, temperature, top_p, external_api_u
         if mime == "application/pdf" or file_bytes[:4] == b"%PDF":
             check_result = check_pdf_structure(file_bytes)
             all_dfs = []
+            saved_header = None
             if check_result > 1:
                 print("➡️ PDF có nhiều cột/nhiều trang → dùng pdfplumber extract trước rồi Gemini.")