fix 机构类型不存在时兼容

mec-biz/src/main/java/com/ym/mec/biz/service/impl/StudentPaymentOrderDetailServiceImpl.java

@@ -145,6 +145,9 @@ public class StudentPaymentOrderDetailServiceImpl extends BaseServiceImpl<Long,
                 goodsIdsStr += studentPaymentOrderDetail.getGoodsIdList() + ",";
             }
         }
+        if(goodsIdsStr.isEmpty()){
+            return null;
+        }
         goodsIdsStr = goodsIdsStr.substring(0, goodsIdsStr.length() - 1);
 
         String[] goodSIdArr = goodsIdsStr.split(",");