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/ResultSetWrapper.java
{
	/**
	 * An internally maintained list containing all rows of raw resultset data
	 */
	final List rawResultSet;
	/**
	 * An internally maintained list containing all working resultset data
	 */
	final List workingResultSet;
	/**
	 * The column expressions associated with the resultset
	 */
	final String[] saExpressionKeys;
	/**
	 * The data types associated with each column in the resultset
	 */
	final int[] iaDataTypes;
	/**
	 * The group breaks associated with all rows of data
	 */
	private int[] iaGroupBreaks = null;
	/**
	 * A lookup table internally used to locate a numeric column index using the
	 * associated expression
	 */
	private final Hashtable htLookup;
	/**