Background Updates: Fix a PHP fatal error which could be encountered on some systems when using FTP.

Merges [26148] from 3.8 to the 3.7 branch.

props dd32.
fixes #25817.


git-svn-id: https://develop.svn.wordpress.org/branches/3.7@27881 602fd350-edb4-49c9-b593-d223f7449a82