Trashing topics theme-side redirects to 404 page

[johnjamesjacoby]

When trashing a topic theme-side, the resulting redirect page is a 404.

Related to: ​https://core.trac.wordpress.org/ticket/11863

This is because bbPress prefetches the redirect_to and does not reprocess it after the topic's slug is changed during the trashing process.

Note that forums & replies do not exhibit the same bug (even though they share similar functionalities) because forums cannot be toggled like topics can, and because replies redirect to the paginated topic URL (and not single reply pages.)

Patch imminent.

[johnjamesjacoby]

In 6269:

Topics: get a fresh value for redirect_to when trashing/untrashing/deleting.

Fixes a bug where trashing a topic theme-side would redirect to the prefetched topic URL and 404.

(In the case of trashed topics, since WordPress 4.7, the slug receives a __trashed suffix, changing the topic link.)

Fixes #3051.