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
* or extension property from extended element of this item.
	 * 
	 * @see org.eclipse.birt.report.model.core.DesignElement#getPropertyDefn(java.lang.String)
	 */
	public ElementPropertyDefn getPropertyDefn( String propName )
	{
		assert propName != null;
		ElementPropertyDefn propDefn = super.getPropertyDefn( propName );
		if ( propDefn != null )
			return propDefn;
		return (ElementPropertyDefn) provider.getPropertyDefn( propName );
	}
	/**
	 * Gets the list of property definitions available to this element. Includes
	 * all properties defined for this element, all user-defined properties
	 * defined on this element or its ancestors, any style properties that this
	 * element supports and extension properties that the extended element of
	 * this item supports.
	 * 
	 * @see org.eclipse.birt.report.model.core.DesignElement#getPropertyDefns()
	 */
	public List getPropertyDefns( )
	{
		if ( props == null )
			props = provider.getPropertyDefns( );
		return props;
	}
	/**
	 * Gets the definition of the extension element.
	 *