[BUG] 在使用SwanLab的OpenAPI时，`get_metrics`函数频繁抛出`list index out of range`错误，导致无法正常获取实验指标数据

[Integer003]

🐛 Bug description [Please make everyone to understand it]

在我使用 SwanLab 的 OpenAPI，尝试将其改写成 MCP Server tools 时，发现经常遇到 get_metric 函数报错 list index out of range 的错误

🧑‍💻 Step to reproduce

1. 获取 SwanLab API
2. 在 terminal 中，执行：

python
>>> from swanlab import OpenApi
>>> api = OpenApi(api_key=<your-swanlab-api-key>)
>>> api.get_summary("BBHCholesky", "55wttnbmav7q1qy9wcoff", "TeaLab")  # parameters description see https://docs.swanlab.cn/api/py-openapi.html#get-summary

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
Cell In[3], line 1
----> 1 api.get_summary("BBHCholesky", "55wttnbmav7q1qy9wcoff", "TeaLab")

File ~/SwanLab/swanlab/api/main.py:210, in OpenApi.get_summary(self, project, exp_id, username)
    208 project_cuid = self.service.get_project_info(username=username, projname=project).data.get("cuid", "")
    209 exp = self.service.get_exp_info(username=username, project=project, exp_id=exp_id)
--> 210 return self.experiment.get_summary(
    211     exp_id=exp_id,
    212     pro_id=project_cuid,
    213     root_exp_id=exp.data.get("rootProId", ""), 
    214     root_pro_id=exp.data.get("rootExpId", "")
    215 )

File ~/SwanLab/swanlab/api/experiment.py:135, in ExperimentAPI.get_summary(self, exp_id, pro_id, root_exp_id, root_pro_id)
    132 if resp.errmsg:
    133     return resp
--> 135 resp.data = list(resp.data.values())[0]
    136 resp.data = {
    137     k: {
    138         "step": v.get("step"),
   (...)
    149     for k, v in resp.data.items()
    150 }
    151 return resp

IndexError: list index out of range