=== modified file 'dhis-2/dhis-api/src/main/java/org/hisp/dhis/period/RelativePeriods.java'
--- dhis-2/dhis-api/src/main/java/org/hisp/dhis/period/RelativePeriods.java	2012-07-30 13:09:47 +0000
+++ dhis-2/dhis-api/src/main/java/org/hisp/dhis/period/RelativePeriods.java	2012-07-31 17:51:33 +0000
@@ -356,7 +356,7 @@
     {
         PeriodType periodType = null;
         
-        if ( periods != null )
+        if ( periods != null && !periods.isEmpty() )
         {            
             PeriodType lowestFrequencyOrder = periods.get( 0 ).getPeriodType();