[Bug] [Module Name] Bug title 'BuiltinKnowledgeGraphConfig' object does not support item assignment

[ghao123]

Search before asking

• I had searched in the issues and found no similar issues.

Operating system information

Linux

Python version information

=3.11

DB-GPT version

main

Related scenes

• Chat Data
• Chat Excel
• Chat DB
• Chat Knowledge
• Model Management
• Dashboard
• Plugins

Installation Information

• Installation From Source

• Docker Installation

• Docker Compose Installation

• Cluster Installation

• AutoDL Image

• Other

Device information

GPU：1
vram：24G

Models information

LLM: DeepSeek-R1-Distill-Qwen-1.5B
Embedding： text2vec-large-chinese

What happened

构建知识库时，选用 Vector Store形式存储知识库时，可正常切片，没有问题；
选用Knowledge Graph时，切片报错“'BuiltinKnowledgeGraphConfig' object does not support item assignment”；

What you expected to happen

dbgpt已更新至main最新版本

How to reproduce

最新版本部署

Additional context

No response

Are you willing to submit PR?

• Yes I am willing to submit a PR!

[Aries-ckt]

http://docs.dbgpt.cn/docs/next/installation/integrations/graph_rag_install

uv sync --all-packages --frozen \
--extra "base" \
--extra "proxy_openai" \
--extra "rag" \
--extra "storage_chromadb" \
--extra "dbgpts"
--extra "graph_rag"

uv run python packages/dbgpt-app/src/dbgpt_app/dbgpt_server.py --config configs/dbgpt-graphrag.toml