[MERGE] Fix a regression on Windows which doesn't allow, listing the empty list of files in a file

[Adrian Wilkins]

Since this patch fixes a regression that's present in 1.6 and hasn't been merged
to bzr.dev yet, IMHO it also needs merging into 1.6 if/when it's merged.

Specifically, it fixes a regression in
robertc at robertcollins.net-20080730095022-4tc7ij34c0tmejb5