Bug 202254 Exception is thrown when category values are null and type of X axis is set to DateTime
chart/org.eclipse.birt.chart.ui.extension/src/org/eclipse/birt/chart/ui/swt/wizard/format/axis/AbstractAxisSubtask.java
getAxisForProcessing( ).setFormatSpecifier( null );
				EList markerLines = getAxisForProcessing( ).getMarkerLines( );
				for ( int i = 0; i < markerLines.size( ); i++ )
				{
					( (MarkerLine) markerLines.get( i ) ).setFormatSpecifier( null );
				}
				EList markerRanges = getAxisForProcessing( ).getMarkerRanges( );
				for ( int i = 0; i < markerRanges.size( ); i++ )
				{
					( (MarkerRange) markerRanges.get( i ) ).setFormatSpecifier( null );
				}
			}
			ChartAdapter.endIgnoreNotifications( );
			
			getAxisForProcessing( ).setType( axisType );
			btnCategoryAxis.setEnabled( !AxisType.TEXT_LITERAL.equals( axisType ) );
			
			refreshPopupSheet( );
		}
		else if ( e.widget.equals( cmbOrigin ) )
		{
			if ( LiteralHelper.intersectionTypeSet.getNameByDisplayName( cmbOrigin.getText( ) )
					.equals( IntersectionType.VALUE_LITERAL.getName( ) ) )
			{
				lblValue.setEnabled( true );
				txtValue.setEnabled( true );
			}
			else
			{
				lblValue.setEnabled( false );