fix docker compose issue (#238)

### What problem does this PR solve?

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

Issue link:#[[Link the issue
here](https://github.com/infiniflow/ragflow/issues/226)]

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

docker/service_conf.yaml

@@ -18,6 +18,7 @@ es:
 user_default_llm:
   factory: 'Tongyi-Qianwen'
   api_key: 'sk-xxxxxxxxxxxxx'
+  base_url: ''
 oauth:
   github:
     client_id: xxxxxxxxxxxxxxxxxxxxxxxxx