I've beening looking into the source for a fix for this one.
SubversiveSession builds a url and includes getHost(). However, this is
not checked for null, a file url has a null host, hence the output. I
would have submitted a patch for this but even after fixing this I still
can't resolve a query against a file url; so I think the problem may be
deeper than this.
I have tried using subversive with a file url and everything works; so
the problem must be in buckminster.