Why won't angular display values that are null when I apply:

```
ng-repeat="p in foo | filter: filter2"

```

where filter2 is 

```
 $scope.filter2 = function(p){
    if (p.state === null){
        return p.state;
    } else{
        return;
    }
};

```

here's a plnkr with what I'm saying: <http://plnkr.co/edit/cj3v1fuBu6sHVI7A4qlq?p=preview>

The filter works when it's anything but a null but I'm trying to only the null ones to display. I could try changing all the null values to a default value string other than a null? Is there anywhere to get the filter to work with nulls?