Bug 136740 Error exporting data from a grouped report.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/ExprManagerUtil.java
while ( it.hasNext( ) )
		{
			String name = it.next( ).toString( );
			Node n = new Node( name );
			IBaseExpression expr = exprManager.getExpr( name );
			if ( expr != null  )
			{
				try
				{
					List l = null;
					if( expr instanceof IScriptExpression )
						l = ExpressionParserUtil.extractColumnExpression( (IScriptExpression)expr );
					else if ( expr instanceof IConditionalExpression )
						l = ExpressionParserUtil.extractColumnExpression( (IConditionalExpression)expr );
					else
						throw new DataException( ResourceConstants.BAD_DATA_EXPRESSION );
					
					for ( int j = 0; j < l.size( ); j++ )
					{
						n.addChild( new Node( l.get( j ) == null?null:l.get( j ).toString( ) ) );
					}
				}
				catch ( BirtException e )
				{
					throw new DataException( e.getLocalizedMessage( ) );
				}
			}
			result.add( n );
		}
		Node[] source = new Node[result.size( )];