Bug 161222 Decoration label should be optional in Gantt Chart
It should not be mandatory to specify a decoration label for Gantt Charts, this can be left blank. Currently the UI and Engine enforce a data definition to be specified for it.
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/internal/datafeed/ResultSetDataSet.java
*/
	private final int[] iaColumnIndexes;
	/**
	 * Bounds of the subset with respect to the parent resultset
	 */
	private final long lStartRow, lEndRow;
	/**
	 * An internal iterator capable of visiting each row in the resultset subset
	 */
	private final Iterator it;
	/**
	 * The current row number being visited
	 */
	private long lRow = 0;
	/**
	 * The parent resultset wrapper of which this instance is a subset
	 */
	private final ResultSetWrapper rsw;
	/**
	 * Temporary variable used in conjunction with the iterator
	 */
	private final Object[] oaTuple;
	/**
	 * Number of columns in this resultset subset
	 */
	private final int iColumnCount;
	private final boolean listMode;
	private final int listDataType;
	/**
	 * The constructor that creates an instance of a resultset subset by