fix ValueError below

File "/home/user/app/app.py", line 154, in chat_with_pdf
for user_msg, ai_msg in history:
ValueError: too many values to unpack (expected 2)

app.py

@@ -151,9 +151,11 @@ async def chat_with_pdf(message, history, state: SessionState):
     rag_chain = create_retrieval_chain(history_aware_retriever, question_answer_chain)
 
     chat_history_for_chain = []
-    for user_msg, ai_msg in history:
-        chat_history_for_chain.append(HumanMessage(content=user_msg))
-        chat_history_for_chain.append(AIMessage(content=ai_msg))
+    for turn in history:
+        if isinstance(turn, (list, tuple)) and len(turn) == 2:
+            user_msg, ai_msg = turn
+            chat_history_for_chain.append(HumanMessage(content=user_msg))
+            chat_history_for_chain.append(AIMessage(content=ai_msg))
 
     response = await rag_chain.ainvoke({
         "chat_history": chat_history_for_chain,
@@ -217,4 +219,4 @@ with gr.Blocks(title="PDF Chatbot") as demo:
         outputs=[chat_row, file_upload_input, state]
     )
 
-demo.launch()
+demo.launch()