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/DataPackage.java
* <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	int SERIES_DEFINITION__FORMAT_SPECIFIER = 3;
	/**
	 * The feature id for the '<em><b>Series</b></em>' containment reference list.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	int SERIES_DEFINITION__SERIES = 4;
	/**
	 * The feature id for the '<em><b>Grouping</b></em>' containment reference.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	int SERIES_DEFINITION__GROUPING = 5;
	/**
	 * The feature id for the '<em><b>Sorting</b></em>' attribute. <!--
	 * begin-user-doc --> <!-- end-user-doc -->
	 * 
	 * @generated
	 * @ordered
	 */
	int SERIES_DEFINITION__SORTING = 6;
	/**
	 * The number of structural features of the '<em>Series Definition</em>' class.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->