Bug with sglang with how the tool call is passed

using custom model provider endpoint of hscn and compactation that was initialized by the model not user initilaized is failing .
Compaction failed. CAPIError: 400 2 validation errors:
{'type': 'literal_error', 'loc': ('body', 'tool_choice', 'ToolChoice', 'type'), 'msg': "Input should be 'function'", 'input': 'none', 'ctx': {'expected': "'function'"}}
{'type': 'literal_error', 'loc': ('body', 'tool_choice', "literal['auto','required','none']"), 'msg': "Input should be 'auto', 'required' or 'none'", 'input': {'function': {'name': ''}, 'type': 'none'}, 'ctx': {'expected': "'auto', 'required' or 'none'"}}

File "/usr/local/lib/python3.12/dist-packages/sglang/srt/entrypoints/http_server.py", line 1491, in openai_v1_chat_completions
POST /v1/chat/completions [{'type': 'literal_error', 'loc': ('body', 'tool_choice', 'ToolChoice', 'type'), 'msg': "Input should be 'function'", 'input': 'none', 'ctx': {'expected': "'function'"}}, {'type': 'literal_error', 'loc': ('body', 'tool_choice', "literal['auto','required','none']"), 'msg': "Input should be 'auto', 'required' or 'none'", 'input': {'function': {'name': ''}, 'type': 'none'}, 'ctx': {'expected': "'auto', 'required' or 'none'"}}]

but when i do /compact manually it works .
idk why .

---
| Field | Value |
| --- | --- |
| App version | 1.1.1 |
| OS | Windows 10.0.26200 |
| Theme | GitHub |
| Path | /chat |
| Tenure | Week 6 |

从已报告的 /compact 行为开始，并将其与失败的模型初始化压缩请求进行比较。检查 sglang/srt/entrypoints/http_server.py 中的 openai_v1_chat_completions，并使用自定义 hscn provider 重现 400 验证错误；当模型初始化的压缩传递有效的 tool_choice，同时手动 /compact 仍能正常工作时，即表示完成。

由索引模型根据 Issue 内容生成。