chore: gemini cr

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: Soulter

astrbot/core/knowledge_base/retrieval/manager.py

@@ -173,7 +173,7 @@ async def retrieve(
         first_rerank = None
         for kb_id in kb_ids:
             vec_db = kb_options[kb_id]["vec_db"]
-            rerank_provider = getattr(vec_db, "rerank_provider", None)
+            rerank_provider = getattr(vec_db, "rerank_provider", None) if vec_db else None
             if rerank_provider is None:
                 continue