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
*/
		EAttribute SERIES_GROUPING__GROUPING_UNIT = eINSTANCE.getSeriesGrouping_GroupingUnit( );
		/**
		 * The meta object literal for the '<em><b>Grouping Origin</b></em>' containment reference feature.
		 * <!-- begin-user-doc -->
		 * <!-- end-user-doc -->
		 * @generated
		 */
		EReference SERIES_GROUPING__GROUPING_ORIGIN = eINSTANCE.getSeriesGrouping_GroupingOrigin( );
		/**
		 * The meta object literal for the '<em><b>Grouping Interval</b></em>' attribute feature.
		 * <!-- begin-user-doc -->
		 * <!-- end-user-doc -->
		 * @generated
		 */
		EAttribute SERIES_GROUPING__GROUPING_INTERVAL = eINSTANCE.getSeriesGrouping_GroupingInterval( );
		/**
		 * The meta object literal for the '<em><b>Group Type</b></em>' attribute feature.
		 * <!-- begin-user-doc -->
		 * <!-- end-user-doc -->
		 * @generated
		 */
		EAttribute SERIES_GROUPING__GROUP_TYPE = eINSTANCE.getSeriesGrouping_GroupType( );
		/**
		 * The meta object literal for the '<em><b>Aggregate Expression</b></em>' attribute feature.
		 * <!-- begin-user-doc -->
		 * <!-- end-user-doc -->
		 * @generated
		 */
		EAttribute SERIES_GROUPING__AGGREGATE_EXPRESSION = eINSTANCE.getSeriesGrouping_AggregateExpression( );