Fix PHP notice: Undefined variable: wp_post_statuss

```
[09-Dec-2013 23:26:32 UTC] PHP Notice:  Undefined variable: wp_post_statuss in /srv/www/vocativ.dev/content/plugins/edit-flow/modules/custom-status/custom-status.php on line 565
[09-Dec-2013 23:26:32 UTC] PHP Warning:  Creating default object from empty value in /srv/www/vocativ.dev/content/plugins/edit-flow/modules/custom-status/custom-status.php on line 566
```

Introduced in 39969cfd48f8cb1220e12f251bdee4e70d6454a0