Deal with errors when calling fs.stat in file-list.js

``fs.stat`` call in ``file-list.js`` does not handle errors. In my case, it failed when finding broken symlinks with ``[TypeError: Cannot call method 'isDirectory' of undefined]``.

At the point of submitting the PR, I just realised this is addressing the exact same issue as #586.
Feel free to disregard if the other solution looks better.