Invalid SQL generated by Doctrine_Query::getLimitSubquery() when ordering by multiple columns

When attempting to order a query by multiple columns I came across this bug. I've attached a reproduction script which will hopefully illustrate the behaviour, but essentially getLimitSubquery() is parsing the order by column incorrectly, leading to an erroneous comma in the sub-select field select clause, e.g

SELECT [m].[id] AS [m__id], [m].[name] AS [m__name], [m].[date] AS [m__date], [r].[id] AS [r__id], [r].[model_id] AS [r__model_id], [r].[name] AS [r__name] FROM [model] [m] INNER JOIN [relation] [r] ON [m].[id] = [r].[model_id] WHERE [m].[id] IN (SELECT TOP 1 [inner_tbl].[id] FROM (SELECT DISTINCT TOP 1 [m].[id], [r].[name],, [r].[id] FROM [model] [m] INNER JOIN [relation] [r] ON [m].[id] = [r].[model_id] ORDER BY [r].[name], [r].[id]) AS [inner_tbl] ORDER BY [inner_tbl].[name] DESC, [inner_tbl].[id] DESC) ORDER BY [r].[name], [r].[id]

(note [r].[name],, [r].[id] - that's the offender).

I've attached a patch against 1.2 HEAD that strips any commas from the fields before they are added to the select clause; it works for me but I'm not sure of all the use cases across the relevant drivers.