Update app.py

app.py

@@ -8,6 +8,7 @@ api_key = "sk-or-v1-5b41e7106feb9b982d4ef5a6aa0959993387ba2e5fc9830df1279418776e
 config = st.text_area("Enter the start URL and the limit of crawling (in this format : URL,limit):")
 config_btn = st.button("Start crawling!")
 
+collection = None
 if config and config_btn:
     global collection
     start = config.split(",")[0]