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/util/DataSwitch.java
return result;
			}
			case DataPackage.BASE_SAMPLE_DATA :
			{
				BaseSampleData baseSampleData = (BaseSampleData) theEObject;
				Object result = caseBaseSampleData( baseSampleData );
				if ( result == null )
					result = defaultCase( theEObject );
				return result;
			}
			case DataPackage.BUBBLE_DATA_SET :
			{
				BubbleDataSet bubbleDataSet = (BubbleDataSet) theEObject;
				Object result = caseBubbleDataSet( bubbleDataSet );
				if ( result == null )
					result = caseDataSet( bubbleDataSet );
				if ( result == null )
					result = defaultCase( theEObject );
				return result;
			}
			case DataPackage.DATA_ELEMENT :
			{
				DataElement dataElement = (DataElement) theEObject;
				Object result = caseDataElement( dataElement );
				if ( result == null )
					result = defaultCase( theEObject );
				return result;
			}
			case DataPackage.DATA_SET :
			{