Fix list index out of range on stream end

app.py

@@ -148,7 +148,8 @@ def stream_answer(query, results, history):
         stream=True,
     )
     for chunk in stream:
-        yield chunk.choices[0].delta.content or ""
+        if chunk.choices:
+            yield chunk.choices[0].delta.content or ""
 
 
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