Bug 202254 Exception is thrown when category values are null and type of X axis is set to DateTime
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/model/data/impl/DataFactoryImpl.java
public StockDataSet createStockDataSet( )
	{
		StockDataSetImpl stockDataSet = new StockDataSetImpl( );
		return stockDataSet;
	}
	/**
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 */
	public TextDataSet createTextDataSet( )
	{
		TextDataSetImpl textDataSet = new TextDataSetImpl( );
		return textDataSet;
	}
	/**
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 */
	public Trigger createTrigger( )
	{
		TriggerImpl trigger = new TriggerImpl( );
		return trigger;
	}
	/**
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	public Object createDataFromString( EDataType eDataType, String initialValue )
	{