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
* 
	 * @param propName
	 *            The name of the property to set. Must be valid. Can be a
	 *            system-defined or user-defined property name.
	 */
	public void clearProperty( String propName )
	{
		setProperty( propName, null );
	}
	/**
	 * Returns the definition object for this element.
	 * <p>
	 * Part of: Meta data system.
	 * 
	 * @return The element definition. Will always be non-null in a valid build.
	 */
	public IElementDefn getDefn( )
	{
		if ( cachedDefn == null )
		{
			cachedDefn = MetaDataDictionary.getInstance( ).getElement(
					getElementName( ) );
			assert cachedDefn != null;
		}
		return cachedDefn;
	}
	/**
	 * Adds a user-defined property. The property must be unique within the
	 * inheritance hierarchy of this element. It cannot duplicate either another
	 * user-defined property or a system-defined property. These checks must