mozilla/zamboni — pull request #2078 by diox (2014-05-20 14:08:30+00:00)
Title: Allow admins to remove all tags (bug 1012649)

https://bugzilla.mozilla.org/show_bug.cgi?id=1012649

`clean_tags` already return an empty set when there are no tags, so that `if` was preventing us from removing all tags from the the addon.