[skip ci]afix shards bug when serch result is empty

shards/mishards/service_handler.py

@@ -61,6 +61,10 @@ class ServiceHandler(milvus_pb2_grpc.MilvusServiceServicer):
                 return status, [], []
 
             row_num = files_collection.row_num
+            # row_num is equal to 0, result is empty
+            if not row_num:
+                continue
+
             ids = files_collection.ids
             diss = files_collection.distances  # distance collections
             # TODO: batch_len is equal to topk, may need to compare with topk
@@ -322,7 +326,7 @@ class ServiceHandler(milvus_pb2_grpc.MilvusServiceServicer):
         topk_result_list = milvus_pb2.TopKQueryResult(
             status=status_pb2.Status(error_code=status.error_code,
                                      reason=status.reason),
-            row_num=len(query_record_array),
+            row_num=len(id_results),
             ids=id_results,
             distances=dis_results)
         return topk_result_list