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
addAnnotation( bubbleDataSetEClass, source, new String[]{
				"name", "BubbleDataSet", 
				"kind", "elementOnly" 
		} );
		addAnnotation( dataEDataType, source, new String[]{
				"name", "Data" 
		} );
		addAnnotation( dataElementEClass, source, new String[]{
				"name", "DataElement", 
				"kind", "empty" 
		} );
		addAnnotation( dataSetEClass, source, new String[]{
				"name", "DataSet", 
				"kind", "elementOnly" 
		} );
		addAnnotation( getDataSet_Values( ), source, new String[]{
				"kind", "element", 
				"name", "Values" 
		} );
		addAnnotation( dateTimeDataElementEClass, source, new String[]{
				"name", "DateTimeDataElement", 
				"kind", "elementOnly" 
		} );
		addAnnotation( getDateTimeDataElement_Value( ), source, new String[]{
				"kind", "element", 
				"name", "Value" 
		} );
		addAnnotation( dateTimeDataSetEClass, source, new String[]{
				"name", "DateTimeDataSet", 
				"kind", "elementOnly"