Poverty level = null generates error in custom reports

Source:  - An error occurred while attempting to run the custom report.
If the problem persists, please contact technical support.
Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or 
when the subquery is used as an expression.
   at jProgBusiness.jBusiness.jSQLDatasetFillHelper.jTableDescriptor.FillTable(DataSet TheDataset, IDbConnection 
Connection, Int32 XMLHandle, jReportSpecification reportSpecification, jKeyLabelPair[] domains)
   at jProgBusiness.jBusiness.jSQLDatasetFillHelper.FillDataset(jServiceManager ServiceManager, ConnectionType 
ConnectionType, Boolean closeConnectionAfterUse, jReportSpecification reportSpecification, jKeyLabelPair[] domains)
   at jProgBusiness.jReports.jCustomReportOperations.getCustomReport(String LoginToken, String ReportSpecPK, 
jKeyLabelPair[] Domains, Boolean showSharedServiceData, String ReportingYear, Boolean ShowNewClientsOnly, 
Boolean ShowSpecification, Boolean SumNumericFields, DateTime DateFrom, DateTime DateThrough, Boolean isCrosstab, 
Boolean showSharedClinicalData, Boolean enforceServiceRestriction, Boolean groupByProvider, 
jCustomReportPrimaryProvider primaryProvider, Boolean appendClientPK, Boolean hidePIIFields)
   at jProgBusiness.jBusiness.jBusinessRemote.CRO_Get_Custom_Report(String SessionToken, String ReportSpecPK, 
jKeyLabelPair[] Domains, Boolean showSharedServiceData, String ReportingYear, Boolean ShowNewClientsOnly, 
Boolean ShowSpecification, Boolean SumNumericFields, DateTime DateFrom, DateTime DateThrough, Boolean isCrosstab, 
Boolean showSharedClinicalData, Boolean groupByProvider, jCustomReportPrimaryProvider primaryProvider, Boolean 
appendClientPK, Boolean hidePIIFields)

Server stack trace:
   at jProgBusiness.jBusiness.jBusinessRemote.CRO_Get_Custom_Report(String SessionToken, String ReportSpecPK, 
jKeyLabelPair[] Domains, Boolean showSharedServiceData, String ReportingYear, Boolean ShowNewClientsOnly, Boolean 
ShowSpecification, Boolean SumNumericFields, DateTime DateFrom, DateTime DateThrough, Boolean isCrosstab, Boolean 
showSharedClinicalData, Boolean groupByProvider, jCustomReportPrimaryProvider primaryProvider, Boolean appendClientPK, 
Boolean hidePIIFields)
   at System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, 
Int32 methodPtr, Boolean fExecuteInContext, Object[]& outArgs)
   at System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(IMessage msg, Int32 methodPtr, Boolean fExecuteInContext)

Exception rethrown at [0]:
   at jProgBusiness.jBusiness.jClientSideRemote.CRO_Get_Custom_Report(String SessionToken, String ReportSpecPK, 
jKeyLabelPair[] Domains, Boolean showSharedServiceData, String ReportingYear, Boolean ShowNewClientsOnly, Boolean 
ShowSpecification, Boolean SumNumericFields, DateTime DateFrom, DateTime DateThrough, Boolean isCrosstab, Boolean 
showSharedClinicalData, Boolean groupByProvider, jCustomReportPrimaryProvider primaryProvider, Boolean appendClientPK, 
Boolean hidePIIFields)
   at Client.CustomReportSetup.fetchReport()
An error occurred while attempting to run the custom report.