With the patch from comment #1 the path is no longer considered relative and the URI passed to createNewDoc is correctly formated. But on Windows, it still fails. Investigating Inkscape::IO::file_test.
With the patch from comment #1 the path is no longer considered relative and the URI passed to createNewDoc is correctly formated. But on Windows, it still fails. :IO::file_ test.
Investigating Inkscape: