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
-1,
				keys,
				serviceprovider,
				getAxisForProcessing( ).getTitle( ).getCaption( ).getValue( ) );
		{
			GridData gd = new GridData( );
			gd.widthHint = 250;
			txtTitle.setLayoutData( gd );
			txtTitle.addListener( this );
		}
		btnTitleVisible = new Button( cmpBasic, SWT.CHECK );
		{
			btnTitleVisible.setText( Messages.getString( "ChartSheetImpl.Label.Visible" ) ); 
			btnTitleVisible.setSelection( getChart( ).getTitle( ).isVisible( ) );
			btnTitleVisible.addSelectionListener( this );
			btnTitleVisible.setSelection( getAxisForProcessing( ).getTitle( )
					.isVisible( ) );
		}
		if ( getAxisAngleType( ) != AngleType.Z )
		{
			Label lblType = new Label( cmpBasic, SWT.NONE );
			lblType.setText( Messages.getString( "OrthogonalAxisDataSheetImpl.Lbl.Type" ) ); 
			cmbTypes = new Combo( cmpBasic, SWT.DROP_DOWN | SWT.READ_ONLY );
			{
				GridData gd = new GridData( );
				gd.widthHint = 220;
				cmbTypes.setLayoutData( gd );
				cmbTypes.addSelectionListener( this );
			}
			btnFormatSpecifier = new Button( cmpBasic, SWT.PUSH );