Bug 213680 [2.2.2]Chart script can not be cleaned completely.
Description: Reset script or delete all script does not work. build version: v20071221-0630 steps to reproduce: 1. New a report. 2. New a chart. 3. Enter some script for the chart and save the report. 4. Click the reset scirpt button or delete all script. 5. Save the report and switch to layout,then switch back to script page. Expected result: Script are cleaned. Actual result: Script are not cleaned. Note: If you delete part of the script, it works.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/elements/ExtendedItem.java
* @return the definition of the extension element if found, or null if the
	 *         extended item is not extensible or the extension element is not
	 *         registered in BIRT
	 */
	public ExtensionElementDefn getExtDefn( )
	{
		return provider.getExtDefn( );
	}
	/**
	 * Creates an instance of <code>IReportItem</code> to store the
	 * information of the peer extension. When the application invokes UI for
	 * the extended item, it calls this method to get the instance of the peer
	 * extension and reads the information--property values from the BIRT ROM
	 * properties. If there is no instance of peer for the item before the
	 * calling and then it is successfully created. If the item has no extension
	 * peer for it or the peer instance has been created before, then there is
	 * no operation.
	 * 
	 * @param module
	 *            the module the peer element has
	 * @throws ExtendedElementException
	 *             if the serialized model is invalid
	 */
	public void initializeReportItem( Module module )
			throws ExtendedElementException
	{
		provider.initializeReportItem( module );
	}
	/**
	 * Returns the extensibility provider which provides the functionality of