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
*/
		EReference SERIES_DEFINITION__GROUPING = eINSTANCE.getSeriesDefinition_Grouping( );
		/**
		 * The meta object literal for the '<em><b>Sorting</b></em>' attribute feature.
		 * <!-- begin-user-doc -->
		 * <!-- end-user-doc -->
		 * @generated
		 */
		EAttribute SERIES_DEFINITION__SORTING = eINSTANCE.getSeriesDefinition_Sorting( );
		/**
		 * The meta object literal for the '{@link org.eclipse.birt.chart.model.data.impl.SeriesGroupingImpl <em>Series Grouping</em>}' class.
		 * <!-- begin-user-doc -->
		 * <!-- end-user-doc -->
		 * @see org.eclipse.birt.chart.model.data.impl.SeriesGroupingImpl
		 * @see org.eclipse.birt.chart.model.data.impl.DataPackageImpl#getSeriesGrouping()
		 * @generated
		 */
		EClass SERIES_GROUPING = eINSTANCE.getSeriesGrouping( );
		/**
		 * The meta object literal for the '<em><b>Enabled</b></em>' attribute feature.
		 * <!-- begin-user-doc -->
		 * <!-- end-user-doc -->
		 * @generated
		 */
		EAttribute SERIES_GROUPING__ENABLED = eINSTANCE.getSeriesGrouping_Enabled( );
		/**
		 * The meta object literal for the '<em><b>Grouping Unit</b></em>' attribute feature.
		 * <!-- begin-user-doc -->
		 * <!-- end-user-doc -->
		 * @generated