fix: handover 合批时创建关系链的bug

apps/wpm/services.py

@@ -710,13 +710,16 @@ def handover_submit(handover:Handover, user: User, now: Union[datetime.datetime,
             batches = [new_batch]
         else:
             raise ParseError("合并批次时请提供新批次号")
+    create_new_batch = False
     for item in handoverb_list:
         wm_from, xcount, handover_or_b = item
 
         # 合并为新批
         if mtype == Handover.H_MERGE:
             batch = new_batch
-            BatchSt.create(batch=batch, handover=handover)
+            if create_new_batch is False:
+                BatchSt.create(batch=batch, handover=handover)
+                create_new_batch = True
             BatchLog.g_create(source_b=wm_from.batch, target_b=batch, handover=handover, relation_type="merge")
         elif mtype == Handover.H_DIV:
             batch = handover_or_b.batch