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
import org.eclipse.birt.chart.model.component.Axis;
import org.eclipse.birt.chart.model.component.ComponentPackage;
import org.eclipse.birt.chart.model.component.MarkerLine;
import org.eclipse.birt.chart.model.component.MarkerRange;
import org.eclipse.birt.chart.model.data.BaseSampleData;
import org.eclipse.birt.chart.model.data.DataElement;
import org.eclipse.birt.chart.model.data.DateTimeDataElement;
import org.eclipse.birt.chart.model.data.NumberDataElement;
import org.eclipse.birt.chart.model.data.OrthogonalSampleData;
import org.eclipse.birt.chart.model.data.impl.DateTimeDataElementImpl;
import org.eclipse.birt.chart.model.data.impl.NumberDataElementImpl;
import org.eclipse.birt.chart.ui.extension.i18n.Messages;
import org.eclipse.birt.chart.ui.swt.composites.ExternalizedTextEditorComposite;
import org.eclipse.birt.chart.ui.swt.composites.FontDefinitionComposite;
import org.eclipse.birt.chart.ui.swt.composites.FormatSpecifierDialog;
import org.eclipse.birt.chart.ui.swt.composites.TextEditorComposite;
import org.eclipse.birt.chart.ui.swt.interfaces.ITaskPopupSheet;
import org.eclipse.birt.chart.ui.swt.interfaces.IUIServiceProvider;
import org.eclipse.birt.chart.ui.swt.wizard.ChartAdapter;
import org.eclipse.birt.chart.ui.swt.wizard.format.SubtaskSheetImpl;
import org.eclipse.birt.chart.ui.swt.wizard.format.popup.InteractivitySheet;
import org.eclipse.birt.chart.ui.swt.wizard.format.popup.axis.AxisGridLinesSheet;
import org.eclipse.birt.chart.ui.swt.wizard.format.popup.axis.AxisLabelSheet;
import org.eclipse.birt.chart.ui.swt.wizard.format.popup.axis.AxisMarkersSheet;
import org.eclipse.birt.chart.ui.swt.wizard.format.popup.axis.AxisScaleSheet;
import org.eclipse.birt.chart.ui.swt.wizard.format.popup.axis.AxisTitleSheet;
import org.eclipse.birt.chart.ui.util.ChartCacheManager;
import org.eclipse.birt.chart.ui.util.ChartUIUtil;
import org.eclipse.birt.chart.ui.util.UIHelper;
import org.eclipse.birt.chart.util.LiteralHelper;