Does lo-dash's `where` ever return `null` or `undefined`? Seems to always return an array, either with items if something is matched, or empty otherwise. Given that no `tag` argument would mean `tag === undefined`, could we simplify the entire function to:

```javascript
var findByTag = function(tag) {
  _reinit();
  return _.where(blogs, { tags: [tag] });
};
```