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
"name", "SeriesGrouping", 
				"kind", "elementOnly" 
		} );
		addAnnotation( getSeriesGrouping_Enabled( ), source, new String[]{
				"kind", "element", 
				"name", "Enabled" 
		} );
		addAnnotation( getSeriesGrouping_GroupingUnit( ), source, new String[]{
				"kind", "element", 
				"name", "GroupingUnit" 
		} );
		addAnnotation( getSeriesGrouping_GroupingOrigin( ),
				source,
				new String[]{
						"kind", "element", 
						"name", "GroupingOrigin" 
				} );
		addAnnotation( getSeriesGrouping_GroupingInterval( ),
				source,
				new String[]{
						"kind", "element", 
						"name", "GroupingInterval" 
				} );
		addAnnotation( getSeriesGrouping_GroupType( ), source, new String[]{
				"kind", "element", 
				"name", "GroupType" 
		} );
		addAnnotation( getSeriesGrouping_AggregateExpression( ),
				source,
				new String[]{