To try you can remove height attribute of your example svg.
Actually i fixe it and make pull request for it fc31c77 .
This worry about only the height, if you do not use width anywhere...
My svg from potrace got attribute viewBox only probably because i use Potracer instead of Potrace.
Certain svg throw this error:
Is there some specification required for the input svg? My svg(path only) was created with potrace.