Bug 152430 Key can modify to empty string
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/PropertyCommand.java
*/
	public void moveItem( MemberRef ref, int oldPosn, int newPosn )
			throws PropertyValueException
	{
		assert ref != null;
		PropertyDefn propDefn = ref.getPropDefn( );
		assert propDefn != null;
		checkListMemberRef( ref );
		List list = ref.getList( module, element );
		if ( list == null )
			throw new PropertyValueException( element, ref.getPropDefn( ),
					null,
					PropertyValueException.DESIGN_EXCEPTION_ITEM_NOT_FOUND );
		ActivityStack stack = getActivityStack( );
		String label = ModelMessages
				.getMessage( MessageConstants.MOVE_ITEM_MESSAGE );
		int adjustedNewPosn = checkAndAdjustPosition( oldPosn, newPosn, list
				.size( ) );
		if ( oldPosn == adjustedNewPosn )
			return;
		stack.startTrans( label );
		makeLocalCompositeValue( ref );
		list = ref.getList( module, element );
		assert list != null;
		MoveListItemRecord record = new MoveListItemRecord( element, ref, list,
				oldPosn, adjustedNewPosn );
		stack.execute( record );
		stack.commit( );
	}
	/**