Do not run prefilter actions if authorizer is destroyed.

This probably wouldn't affect a production application, but in testing if you create new containers to test with (or if you reset your application), you could end up with many pre-filters set up. Since there's no way to remove a pre-filter, I think this is a good way to keep them from running once the authorizer and container are no longer in use.
I'd move that to line 138

```js
if (!!authorizer && !authorizer.isDestroyed) {
```

Can you also add a test for that?