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
oContent, new Integer( iDataType )
					} )
			);
		}
		if ( co != null )
		{
			it = co.iterator( );
		}
		iRowCount = getRowCountInternal( );
	}
	/**
	 * 
	 * @param ds
	 * @throws UnexpectedInputException
	 */
	public DataSetIterator( DataSet ds ) throws IllegalArgumentException,
			ChartException
	{
		Object oContent = ds.getValues( );
		if ( ds instanceof NumberDataSet )
		{
			iDataType = IConstants.NUMERICAL;
			if ( oContent instanceof Collection )
			{
				iContentType = IConstants.COLLECTION;
				co = (Collection) oContent;
			}
			else if ( oContent instanceof double[] )
			{
				iContentType = IConstants.PRIMITIVE_ARRAY;