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/DataPackageImpl.java
/**
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 */
	private EClass triggerEClass = null;
	/**
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	private EDataType dataEDataType = null;
	/**
	 * Creates an instance of the model <b>Package </b>, registered with
	 * {@link org.eclipse.emf.ecore.EPackage.Registry EPackage.Registry}by the
	 * package package URI value.
	 * <p>
	 * Note: the correct way to create the package is via the static factory
	 * method {@link #init init()}, which also performs initialization of the
	 * package, or returns the registered package, if one already exists. <!--
	 * begin-user-doc --> <!-- end-user-doc -->
	 * 
	 * @see org.eclipse.emf.ecore.EPackage.Registry
	 * @see org.eclipse.birt.chart.model.data.DataPackage#eNS_URI
	 * @see #init()
	 * @generated
	 */
	private DataPackageImpl( )
	{
		super( eNS_URI, DataFactory.eINSTANCE );
	}