Update app.py

app.py

@@ -128,7 +128,7 @@ async def gen_show(script):
 
 @spaces.GPU(duration=100)
 async def generator(link):
-    if not link.startswith("http://") and not article_url.startswith("https://"):
+    if not link.startswith("http://") and not link.startswith("https://"):
         return "URL must start with 'http://' or 'https://'",None
 
     text = fetch_text(link)