Fix JSHint errors in media-upload.js.

props iblamefish.
fixes #26023.


git-svn-id: https://develop.svn.wordpress.org/trunk@26196 602fd350-edb4-49c9-b593-d223f7449a82
Fix JSHint errors in heartbeat.js.

props dziudek.
fixes #25986.


git-svn-id: https://develop.svn.wordpress.org/trunk@26197 602fd350-edb4-49c9-b593-d223f7449a82