Bug 136027 [Smoke]the report with a gounp can not preview
Description: the report with a gounp can not preview Steps to reproduce: 1. new a datasource and a dataset 2. drag the dataset to the layout 3. Add a group on the table. save and preview. Actual result: "Error happened while running the report" is appeared.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/GroupDialog.java
}
				if ( slotHandle != null && index != -1 )
				{
					DataItemHandle dataItemHandle = inputGroup.getElementFactory( )
							.newDataItem( null );
					dataItemHandle.setResultSetColumn( ( (ComputedColumnHandle) columnList.get( index ) ).getName( ) );
					slotHandle.add( dataItemHandle );
				}
			}
			index = intervalType.getSelectionIndex( );
			inputGroup.setInterval( intervalChoices[index].getName( ) );
			if ( index != 0 )
			{
				inputGroup.setIntervalRange( intervalRange.getSelection( ) );
			}
			else
			{
				inputGroup.setProperty( GroupHandle.INTERVAL_RANGE_PROP, null );