can.Model Fails Silently When Server Doesn't Return an Array for findAll

No deferred method is executed if invalid data is returned. For example:

```javascript
myModel.findAll({myData: 'myValue'}, function(result) {
    // do something here
}).fail(function(xhr, textStatus, errorThrown) {
  // do something here
});
```
Success callback or fail callback not called. This hold true for 'then'.