Bug 156632 [Acceptance]Cannot paste theme when select Themes in Outline.
Description: Cannot paste theme when select Themes in Outline. Steps to reproduce: 1. New a library. 2. Select defaulttheme in outline and cut it 3. Select Themes and right click to paste the theme back. Expected result: Paste in context menu can be used. Actual result: Paste is gray
UI/org.eclipse.birt.report.designer.core/src/org/eclipse/birt/report/designer/util/DNDUtil.java
*            container, not null
	 * @param handle
	 *            new object. If new object is null, create nothing
	 * @throws SemanticException
	 */
	public static void addElementHandle( Object container,
			DesignElementHandle handle ) throws SemanticException
	{
		assert ( container != null );
		if ( handle == null )
		{
			return;
		}
		container = unwrapToModel( container );
		if ( container instanceof DesignElementHandle )
		{
			( (DesignElementHandle) container ).addElement( handle,
					DEUtil.getDefaultSlotID( container ) );
		}
		else if ( container instanceof SlotHandle )
		{
			( (SlotHandle) container ).add( handle );
		}
	}
	public static void addEmbeddedImageHandle( Object container,
			EmbeddedImage image ) throws SemanticException
	{
		if ( container instanceof EmbeddedImageNode )
		{
			container = ( (EmbeddedImageNode) container ).getReportDesignHandle( );