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
* 
	 * @param obj
	 * @return the length of elements in object
	 */
	public static int getObjectLength( Object obj )
	{
		if ( obj == null )
		{
			return 0;
		}
		else if ( obj instanceof StructuredSelection )
		{
			return getObjectLength( ( (StructuredSelection) obj ).toArray( ) );
		}
		else if ( obj instanceof Object[] )
		{
			return ( (Object[]) obj ).length;
		}
		return 1;
	}
	/**
	 * Checks whether child's container exists in handle array
	 * 
	 * @param content
	 *            child handle
	 * @param handles
	 *            handle array
	 * @return if exists
	 */
	public static boolean checkContainerExists( Object content, Object[] handles )