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
txtValue.setEnabled( false );
			}
			getAxisForProcessing( ).getOrigin( )
					.setType( IntersectionType.getByName( LiteralHelper.intersectionTypeSet.getNameByDisplayName( cmbOrigin.getText( ) ) ) );
		}
		else if ( e.widget.equals( btnCategoryAxis ) )
		{
			getAxisForProcessing( ).setCategoryAxis( btnCategoryAxis.getSelection( ) );
			ChartCacheManager.getInstance( )
					.cacheCategory( ( (ChartWithAxes) getChart( ) ).getType( ),
							btnCategoryAxis.getSelection( ) );
			refreshPopupSheet( );
		}
		else if ( e.widget.equals( btnTitleVisible ) )
		{
			getAxisForProcessing( ).getTitle( )
					.setVisible( btnTitleVisible.getSelection( ) );
			setStateOfTitle( );
			if ( !btnTitleVisible.getSelection( )
					&& btnAxisTitle.getSelection( ) )
			{
				btnAxisTitle.setSelection( false );
				detachPopup( btnAxisTitle );
			}
			else
			{
				refreshPopupSheet( );
			}
		}
		else if ( e.widget.equals( btnLabelVisible ) )