I'm having an issue with subreports in when writing a report for Log

I have a primary report with a search for workflows initiated by user
X. One of the fields in this report is evtgrpid (Name of data from
sentinel and name of field).

I then added a subreport, with a parameter called EVT_ID. In the
subreport mapping in the parent report, I set the parameter EVT_ID to
the value $F{evntgrpid}

My query on the sub-report is

select msg as sub_msg where ((identitymanager) and (rv52:"NOTIFY")) AND

I get the error:

Error generating report: java.lang.NullPointerException at:
com.novell.reports.jasper.data.event.LuceneEventQu eryExecutor.getParameterReplacement(LuceveEventQue ryExecutor.java:206)....