fix prompt

app.py

@@ -3,9 +3,8 @@ import streamlit as st
 from transformers import pipeline
 
 classifier = pipeline("sentiment-analysis")
-output = classifier("We are very happy to show you the 🤗 Transformers library.")
 
 prompt = st.chat_input("Say something")
-output = classifier(prompt)
 if prompt:
+    output = classifier(prompt)
     st.write(f"User has sent the following prompt: {output}")