Avoid PHP notice on blank chat lines. props SergeyBiryukov. see #23625

git-svn-id: http://core.svn.wordpress.org/trunk@23880 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Logged out warnings: by default, load only in the admin. Plugins and themes can load on the front-end when needed, see #23295

git-svn-id: http://core.svn.wordpress.org/trunk@23881 1a063a9b-81f0-0310-95a4-ce76da25c4cd