Update app.py

app.py

@@ -78,7 +78,10 @@ def main():
     st.header("Chat with multiple PDFs :books:")
     user_question = st.text_input("Ask a question about your documents:")
     if user_question:
-        handle_userinput(user_question)
+        if st.session_state.conversation is None:
+            st.warning("Please upload and process your PDFs first.")
+        else
+            handle_userinput(user_question)
 
     with st.sidebar:
         st.subheader("Your documents")