bugfix:房间信息-从校区同步创建的区域，没有挂在族级区域下面，无法添加子区域

ruoyi-modules/ruoyi-backstage/src/main/java/org/dromara/backstage/basics/service/impl/PtAreaServiceImpl.java

@@ -129,6 +129,8 @@ public class PtAreaServiceImpl implements IPtAreaService {
             PtArea parent = baseMapper.selectById(bo.getParentId());
             if(parent!=null){
                 add.setAncestors(parent.getAncestors()+","+parent.getAreaId());
+            }else{
+                throw new ServiceException("父节点不存在");
             }
         }
     }