Fix: infinity rerank error. (infiniflow#10760)

### Type of change

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

Author: KevinHuSh

rag/nlp/search.py

@@ -388,6 +388,7 @@ def retrieval(self, question, embd_mdl, tenant_ids, kb_ids, page, page_size, sim
             else:
                 # Don't need rerank here since Infinity normalizes each way score before fusion.
                 sim = [sres.field[id].get("_score", 0.0) for id in sres.ids]
+                sim = [s if s is not None else 0. for s in sim]
                 tsim = sim
                 vsim = sim
         # Already paginated in search function