Segfaults when opening bare git repository

Steps to reproduce (on arch):

git clone repo --bare dir
juci dir
Segmentation fault (core dumped)

The segfault happens here:

boost::filesystem::path Git::Repository::get_work_path() noexcept {
  std::lock_guard<std::mutex> lock(mutex);
  // because repository is nullptr
  return Git::path(git_repository_workdir(repository.get()));
}

@eidheim Could you take a look at this since I'm not familiar with libgit2?