gitstatus.py : issue with empty repositories

[squalou]

I faced a funny situation after cloning an empty repo : here's the display

[No|MERGING|✔]$ ll
git_super_status:[:23: integer expression expected: yet                                                                                                                                                             
git_super_status:[:23: integer expression expected: commits
git_super_status:[:26: integer expression expected: yet
git_super_status:[:29: integer expression expected: commits
git_super_status:[:35: integer expression expected: on
git_super_status:[:39: integer expression expected: master

I bet some other weird situations may happen in broken repos or some other unusual situation.

Not a big deal, more a 'nice to have' than anything.

Regards.