repo.branch fails on empty repo

issue22.js

var git = require('nodegit');
git.repo().init("foo", true, function() {
  git.repo("foo", function(err, repo) {
    repo.branch("master", function(err, branch) {
      console.log({
        err: err,
        branch: branch
      });
      console.log("doing something else");
    });
  });
});
/*
{ err: { error: {} },
  branch: 
   { repo: {},
     ref: {},
     lookup: [Function],
     oid: [Function] } }
doing something else
node: ../../src/refs.c:1067: git_reference_oid: Assertion `ref' failed.
*/