Unable to get reference for HEAD

When I try to get the reference for 'HEAD' in version 0.2.3:

``` js
repo.getReference('HEAD').then(function() {
  console.log('success');
}, function() {
  console.log('error');
});
```

I do not see 'success' nor 'error'. It just doesn't do anything. If it fails, I would expect to see 'error'..
