Fix error response (#3719)

### What problem does this PR solve?



### Type of change

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

---------

Co-authored-by: Jin Hai <haijin.chn@gmail.com>

rag/llm/rerank_model.py

@@ -158,6 +158,8 @@ class XInferenceRerank(Base):
     def __init__(self, key="xxxxxxx", model_name="", base_url=""):
         if base_url.find("/v1") == -1:
             base_url = urljoin(base_url, "/v1/rerank")
+        if base_url.find("/rerank") == -1:
+            base_url = urljoin(base_url, "/v1/rerank")
         self.model_name = model_name
         self.base_url = base_url
         self.headers = {