Bug 136241 [regression]Preview template in web viewer and pdf didn't get correct effect.
Description: Preview template items in web viewer and pdf didn't get correct effect. Steps to reproduce: 1. Create template items. 2. Preview in Web Viewer and pdf. Expected result: Same effect as in html. Actual result: In web viewer, see only blank box. In pdf, blank page.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
*            <code>null</code>.
	 * @throws PropertyValueException
	 *             if the structure list or the structure to add has any
	 *             semantic error..
	 */
	public void checkStructureList( Module module, PropertyDefn propDefn,
			List list, IStructure toAdd ) throws PropertyValueException
	{
		List errorList = StructureListValidator.getInstance( )
				.validateForAdding( getHandle( module ), propDefn, list, toAdd );
		if ( errorList.size( ) > 0 )
		{
			throw (PropertyValueException) errorList.get( 0 );
		}
	}
	/**
	 * Checks the parent element.
	 * 
	 * @param parent
	 *            the parent element
	 * @return <true> if the parent element is <code>NOT_FOUND</code>,<code>WRONG_TYPE</code>,
	 *         <code>SELF_EXTEND</code>,<code>CIRCULAR</code>. Otherwise
	 *         <code>false</code>.
	 */
	private boolean isExtendsValid( DesignElement parent )
	{
		try
		{
			checkExtends( parent );
		}