差旅费用报销单扩展之后打开单据报错

日志报错信息：
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException: Object reference not set to an instance of an object.
at Kingdee.BOS.Core.Metadata.FieldElement.DecimalFieldAppearance.GetBindValue(ControlBindValueArgs arg)
at Kingdee.BOS.Core.Metadata.EntityElement.EntryEntityAppearance.GetRowBindValue(ControlBindValueArgs arg, String seqFieldKey, List`1 fieldsAp)
at Kingdee.BOS.Core.Metadata.EntityElement.EntryEntityAppearance.GetBindValue(ControlBindValueArgs arg)
at Kingdee.BOS.Web.DynamicForm.DataBinder.BindControlData(ControlAppearance ctl, Int32 row)
at Kingdee.BOS.Web.DynamicForm.DataBinder.BindControlData(ControlAppearance ctl)
at Kingdee.BOS.Web.DynamicForm.DataBinder.BindControlsData(List`1 list)
at Kingdee.BOS.Web.DynamicForm.DataBinder.BindControlData(ControlAppearance ctl)
at Kingdee.BOS.Web.DynamicForm.DataBinder.BindControlsData(List`1 list)
at Kingdee.BOS.Web.DynamicForm.DataBinder.UpdateView()
at Kingdee.BOS.Web.DynamicForm.AbstractDynamicWebFormView.UpdateView()
at Kingdee.BOS.Web.Bill.BillView.UpdateView()
at Kingdee.BOS.Web.Bill.BillView.LoadData()
at Kingdee.BOS.Web.DynamicForm.DynamicWebFormController.LoadData()
--- End of inner exception stack trace ---

打开扩展报错：