Do not attempt a slide transition if the current and switched-to post
formats both have no UI. Do not slide if clicking on the current format.

see #19570

git-svn-id: https://core.svn.wordpress.org/trunk@23854 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Remove duplicated code that was accidentally committed in [23417].

fixes #23889. props DrewAPicture.

git-svn-id: https://core.svn.wordpress.org/trunk@23855 1a063a9b-81f0-0310-95a4-ce76da25c4cd