Kill zombie windows

As described in #52, we have a zombie window problem:

1. Open a survey from a notification
2. Close the survey without submitting a form
3. Open another survey from the notification
4. The old survey that you closed will re-open (!!!)

This adds a hack to re-close all of the zombies as soon as they reopen.
So even if you kill the zombie, the previously killed zombies appear next time? That's very weird. I'll try to reproduce this tomorrow.

Btw I think you should name this concept "zombie invariant" and submit to the standards committe :)