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
}
		ITaskPopupSheet popup;
		if ( getAxisAngleType( ) != AngleType.Z )
		{
			
			popup = new AxisScaleSheet( Messages.getString( "AxisYSheetImpl.Label.Scale" ), 
					getContext( ),
					getAxisForProcessing( ),
					getAxisAngleType( ) );
			Button btnScale = createToggleButton( cmp,
					Messages.getString( "AxisYSheetImpl.Label.Scale&" ), 
					popup );
			btnScale.addSelectionListener( this );
		}
		
		popup = new AxisTitleSheet( Messages.getString( "AxisYSheetImpl.Label.TitleFormat" ), 
				getContext( ),
				getAxisForProcessing( ),
				getAxisAngleType( ) );
		btnAxisTitle = createToggleButton( cmp,
				Messages.getString( "AxisYSheetImpl.Label.TitleFormat&" ), 
				popup );
		btnAxisTitle.addSelectionListener( this );
		btnAxisTitle.setEnabled( btnTitleVisible.getSelection( ) );
		
		popup = new AxisLabelSheet( Messages.getString( "AxisYSheetImpl.Label.LabelFormat" ), 
				getContext( ),
				getAxisForProcessing( ),
				getAxisAngleType( ) );
		btnAxisLabel = createToggleButton( cmp,