Bug 210609 [Smoke]Crosstab is failed to preview in runtime
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/extension/ExtendedElementUIPoint.java
* Gets the corresponding attribute of the key of the extended element
	 * 
	 * @param key
	 *            the key of the attribute. It cannot be null. One of the constants
	 *  defined in IExtensionConstants
	 * 				
	 * @return Returns the corresponding attribute, or null if the key is
	 *         invalid or the corresponding attribute hasn't been set
	 */
	public Object getAttribute(String key) {
		Assert.isLegal(key != null);
		return attributesMap.get(key);
	}
	/**
	 * Sets the UI instance of the element
	 * 
	 * @param reportItemUI
	 *            the UI instance to set.It cannot be null
	 */
	void setReportItemUI(IReportItemFigureProvider reportItemUI) {
		Assert.isLegal(reportItemUI != null);
		this.reportItemUI = reportItemUI;
	}
	/**
	 * Sets the UI instance of the element
	 * 
	 * @param reportItemBuilderUI
	 *            the Builder UI instance to set.It can be null
	 */
	void setReportItemBuilderUI(IReportItemBuilderUI reportItemBuilderUI) {