joomla/joomla-cms — pull request #3607 by infograf768 (2014-05-17 08:42:15+00:00)
Title: Administrator lang strings overrides can't be deleted

Create new strings overrides for a site language AND for an admin language
administrator/index.php?option=com_languages&view=overrides

Try to delete the site language override. All is fine.
Try to delete the admin language override. Although the message displays that the string has been deleted, it is not and still showing in the manager.
The issue comes from the fact that the $client is not found and always null

This should solve the issue.