Fitin for infinity. (#4722)

### What problem does this PR solve?

### Type of change

- [x] Refactoring

graphrag/search.py

 
     def _ent_info_from_(self, es_res, sim_thr=0.3):
         res = {}
-        es_res = self.dataStore.getFields(es_res, ["content_with_weight", "_score", "entity_kwd", "rank_flt",
-                                                   "n_hop_with_weight"])
+        flds = ["content_with_weight", "_score", "entity_kwd", "rank_flt", "n_hop_with_weight"]
+        es_res = self.dataStore.getFields(es_res, flds)
         for _, ent in es_res.items():
+            for f in flds:
+                if f in ent and ent[f] is None:
+                    del ent[f]
             if float(ent.get("_score", 0)) < sim_thr:
                 continue
             if isinstance(ent["entity_kwd"], list):

rag/utils/infinity_conn.py

         if matchExprs:
             selectFields.append(score_func)
             selectFields.append(PAGERANK_FLD)
+        selectFields = [f for f in selectFields if f != "_score"]
 
         # Prepare expressions common to all tables
         filter_cond = None
         if matchExprs:
             res = res.sort(pl.col(score_column) + pl.col(PAGERANK_FLD), descending=True, maintain_order=True)
             if score_column and score_column != "SCORE":
-                res = res.rename({score_column: "SCORE"})
+                res = res.rename({score_column: "_score"})
         res = res.limit(limit)
         logger.debug(f"INFINITY search final result: {str(res)}")
         return res, total_hits_count