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
* The meta object id for the '{@link org.eclipse.birt.chart.model.data.impl.SeriesDefinitionImpl <em>Series Definition</em>}' class.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.data.impl.SeriesDefinitionImpl
	 * @see org.eclipse.birt.chart.model.data.impl.DataPackageImpl#getSeriesDefinition()
	 * @generated
	 */
	int SERIES_DEFINITION = 15;
	/**
	 * The feature id for the '<em><b>Query</b></em>' containment reference.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	int SERIES_DEFINITION__QUERY = 0;
	/**
	 * The feature id for the '<em><b>Series Palette</b></em>' containment reference.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	int SERIES_DEFINITION__SERIES_PALETTE = 1;
	/**
	 * The feature id for the '<em><b>Series Definitions</b></em>' containment reference list.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	int SERIES_DEFINITION__SERIES_DEFINITIONS = 2;
	/**
	 * The feature id for the '<em><b>Format Specifier</b></em>' containment reference.