Bug 191637 Empty cube causes error
Comment removed as requested by the submitter - 2007-06-08 droy
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/olap/data/util/DiskIndex.java
documentObject.seek( currentNode.offset );
			for ( int j = 0; j < currentNode.numberOfSon; j++ )
			{
				IndexKey indexKey = readKeyObject( );
				for ( int k = 0; k < selectionMark.length; k++ )
				{
					if ( selectionMark[k] )
					{
						if ( selections[k].isSelected( indexKey.getKey() ) )
						{
							resultList.add( indexKey );
							break;
						}
					}
				}
			}
		}
		return resultList;
	}
	
	/**
	 * 
	 * @param n
	 * @return
	 * @throws IOException
	 */
	public IDiskArray topN( int n ) throws IOException
	{
		BufferedStructureArray resultList = new BufferedStructureArray( IndexKey.getCreator( ),
				Math.min( n, Constants.MAX_LIST_BUFFER_SIZE ) );