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 slotId
	 *            the slot id of the container element
	 * @param defn
	 *            the element definition
	 * @return <code>true</code> if this insertion is valid. Otherwise
	 *         <code>false</code>.
	 */
	protected List checkContent( Module module, DesignElement container,
			int slotId, IElementDefn defn )
	{
		return new ArrayList( );
	}
	/**
	 * Returns the slot within the container element that holds this element.
	 * 
	 * @return the container's slot in which this element appears
	 */
	public int getContainerSlot( )
	{
		return containerSlotID;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.core.IPropertySet#getObjectDefn()
	 */
	public IObjectDefn getObjectDefn( )
	{
		return getDefn( );
	}