fix default reason

app.py

@@ -107,7 +107,7 @@ def completion():
         }, headers={"Authorization": f"Bearer {st.secrets['token']}"})
         answer = resp.json()
         for idx, choice in enumerate(answer['choices']):
-            if choice.get("finish_reason", "finished") != "finished":
+            if choice.get("finish_reason", None) != "finished":
                 st.error(f'生成结果#{idx}出错: {choice["finish_reason"]}')
             elif choice.get("text", None) is None:
                 st.error(f'生成结果#{idx}出错: 无生成结果')