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.util.NameSet;
import org.eclipse.birt.chart.util.TriggerSupportMatrix;
import org.eclipse.emf.common.util.EList;
import org.eclipse.jface.window.Window;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Combo;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Listener;
import com.ibm.icu.text.NumberFormat;
import com.ibm.icu.text.SimpleDateFormat;
import com.ibm.icu.util.Calendar;
import com.ibm.icu.util.TimeZone;
/**
 * Axis subtask
 * 
 */
abstract class AbstractAxisSubtask extends SubtaskSheetImpl implements
		Listener,
		SelectionListener
{
	private Button btnCategoryAxis;
	private ExternalizedTextEditorComposite txtTitle;
	private Button btnTitleVisible;