Blank page opens via un-/subscribe link in new window/tab

Steps to reproduce
User is subscribed.

1. Open a forum page.
2. Click unsubscribe link on a page in a new tab/window. User is unsubscribed.

AR: New blank page appears.
ER: As a result forum page with subscribe link appears.

User is unsubscribed.

1. Open a forum page.
2. Click subscribe link on a page in a new tab/window. User is subscribed.

AR: New blank page appears.
ER: Forum page with unsubscribe link appears .