Update app.py

app.py

@@ -33,7 +33,8 @@ def respond(message, chat_history):
                                                "maximal_marginal_relevance":True,
                                                "k":10})
 
-    chat_history = chat_history[1]
+    if len(chat_history) == 0: 
+        chat_history = chat_history[1]
     
     # Create ChatOpenAI and ConversationalRetrievalChain
     model = ChatOpenAI(model='gpt-3.5-turbo')