Bug 152430 Key can modify to empty string
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/CustomColorHandle.java
{
	/**
	 * Constructs the handle of custom color.
	 * 
	 * @param valueHandle
	 *            the value handle for custom color list of one property
	 * @param index
	 *            the position of this custom color in the list
	 */
	public CustomColorHandle( SimpleValueHandle valueHandle, int index )
	{
		super( valueHandle, index );
	}
	/**