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( ).getLabel( )
					.setVisible( btnLabelVisible.getSelection( ) );
			setStateOfLabel( );
			if ( !btnLabelVisible.getSelection( )
					&& btnAxisLabel.getSelection( ) )
			{
				btnAxisLabel.setSelection( false );
				detachPopup( btnAxisLabel );
			}
			else
			{
				refreshPopupSheet( );
			}
		}
		else if ( e.widget.equals( btnFormatSpecifier ) )
		{
			String sAxisTitle = Messages.getString( "OrthogonalAxisDataSheetImpl.Lbl.OrthogonalAxis" ); 
			try
			{
				String sTitleString = getAxisForProcessing( ).getTitle( )
						.getCaption( )
						.getValue( );
				int iSeparatorIndex = sTitleString.indexOf( ExternalizedTextEditorComposite.SEPARATOR );
				if ( iSeparatorIndex > 0 )
				{
					sTitleString = sTitleString.substring( iSeparatorIndex );
				}
				else if ( iSeparatorIndex == 0 )
				{