how to fill NULL in dashboard when element is not occurred in XML

Hello, I have following XML loaded into filed 'data'. Strin2String5String7 I am able to extract the 'stepEventName', 'nextEventNam' element values using below spath: spath input=data output=StepEvent path=SummaryEvent.StepEvent.stepEventName | spath input=data output=NextEvent path=SummaryEvent.StepEvent.nextEventName | eval x=mvzip(NextEvent,StepEvent) | mvexpand x| eval x=split(x,",") | eval NextEvent=mvindex(x,0) | eval StepEvent=mvindex(x,1) | fillnull value="NULL" |table NextEvent,StepEvent But when i try to display event list i do get below since nextEventName occured once in 'Step' ------------------------------------- _time NextEvent StepEvent ------------------------------------- timestamp String5 String2 But the below is what i want to display. ------------------------------------- _time NextEvent StepEvent ------------------------------------- timestamp String5 String2 timestamp NULL String5 How to get the NULL when nextEventName is not occured in 'Step' Thanks in Advance