Bug 142928 Item from library is changed to a report design item after revert to report item
Details: Item from library is changed to a report design item after revert to report item. Setp: 1.New a template. 2.Use a libary contain a label. 3.Drop the label from library explorer into layout. 4.Change the label to template item. 5.Revert the template item to report item. Actual result: The label is become a report item, but a item from library. Please see the attach image. Exception result: The lable is revert a item from library.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/DesignElementHandle.java
* Returns the a handle the the container's slot that holds this element.
	 * 
	 * @return the slot handle in which this element resides, <code>null</code>
	 *         if this element has no container.
	 */
	public SlotHandle getContainerSlotHandle( )
	{
		DesignElementHandle containerHandle = getContainer( );
		if ( containerHandle == null )
			return null;
		int slotID = containerHandle.findContentSlot( this );
		assert slotID != DesignElement.NO_SLOT;
		return containerHandle.getSlot( slotID );
	}
	/**
	 * Returns a handle to the given slot. If this element has no such slot,
	 * <code>null</code> will be returned.
	 * 
	 * @param slotID
	 *            the identifier of the slot for which to obtain a handle
	 * @return the handle for the requested slot
	 */
	public SlotHandle getSlot( int slotID )
	{
		int slotCount = getDefn( ).getSlotCount( );
		if ( slotCount == 0 )
		{
			return null;
		}
		assert 0 <= slotID && slotID < slotCount;