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
*            base element.
	 */
	public void setExtendsElement( DesignElement base )
	{
		DesignElement oldExtends = getExtendsElement( );
		if ( base == oldExtends )
			return;
		if ( oldExtends != null )
			oldExtends.dropDerived( this );
		if ( base == null )
		{
			extendsRef = null;
		}
		else
		{
			
			assert base.getDefn( ) == getDefn( );
			
			assert base.getName( ) != null;
			String namespace = null;
			Module root = base.getRoot( );
			if ( root instanceof Library )
			{
				namespace = ( (Library) root ).getNamespace( );
			}
			extendsRef = new ElementRefValue( namespace, base );
			base.addDerived( this );
		}
	}
	/**