Add missing inline descriptions.

props momo360modena, aaronholbrook.
see #20494, fixes #23304.

git-svn-id: http://core.svn.wordpress.org/trunk@23350 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Make sure the post exists before checking its ID. fixes #23026.

git-svn-id: http://core.svn.wordpress.org/trunk@23351 1a063a9b-81f0-0310-95a4-ce76da25c4cd