It looks like `where` defaults to no results if [`_.isEmpty(conditions)`](https://github.com/jashkenas/underscore/blob/master/underscore.js#L246), so replacing this filter with it won't work:

```
coffee> u.where [{a:'b'}], {a:'b'}
[ { a: 'b' } ]
coffee> u.where [{a:'b'}], {}
[]
coffee> u.where [{a:'b'}], undefined
[]
coffee> u.where [{a:'b'}], null
[]
coffee> u.where [{a:'b'}], true
[]
```