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/computation/DataSetIterator.java
da = (double[]) oContent;
			}
			else if ( oContent instanceof Double[] )
			{
				iContentType = IConstants.NON_PRIMITIVE_ARRAY;
				dda = (Double[]) oContent;
			}
			else if ( oContent instanceof Number )
			{
				iContentType = IConstants.PRIMITIVE_ARRAY;
				da = new double[]{
					( (Number) oContent ).doubleValue( )
				};
			}
		}
		else if ( ds instanceof DateTimeDataSet )
		{
			iDataType = IConstants.DATE_TIME;
			if ( oContent instanceof Collection )
			{
				iContentType = IConstants.COLLECTION;
				co = (Collection) oContent;
			}
			else if ( oContent instanceof long[] )
			{
				iContentType = IConstants.PRIMITIVE_ARRAY;
				la = (long[]) oContent;
				cReused = Calendar.getInstance( );
			}
			else if ( oContent instanceof Calendar[] )