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/DataAdapterFactory.java
{
			return createBubbleDataSetAdapter( );
		}
		public Object caseDataElement( DataElement object )
		{
			return createDataElementAdapter( );
		}
		public Object caseDataSet( DataSet object )
		{
			return createDataSetAdapter( );
		}
		public Object caseDateTimeDataElement( DateTimeDataElement object )
		{
			return createDateTimeDataElementAdapter( );
		}
		public Object caseDateTimeDataSet( DateTimeDataSet object )
		{
			return createDateTimeDataSetAdapter( );
		}
		public Object caseDifferenceDataSet( DifferenceDataSet object )
		{
			return createDifferenceDataSetAdapter( );
		}
		public Object caseGanttDataSet( GanttDataSet object )
		{
			return createGanttDataSetAdapter( );
		}
		public Object caseNumberDataElement( NumberDataElement object )
		{
			return createNumberDataElementAdapter( );