add

OASystem/OASystem.Api/Controllers/GroupsController.cs

@@ -5531,7 +5531,7 @@ FROM
                         Remark = item.Remark,
                         STid = item.STid,
                     },
-                    Child = JsonConvert.DeserializeObject<List<string>>(item.Remark)
+                    Child = JsonConvert.DeserializeObject<List<string>>(item.Remark) ?? new List<string>()
                 });
             }