Found a fix for this!
Since it does work, even though it reports this error, the way to work around it (I admit, it’s technically sloppy), is to hide the error.
1) Open wp-admin/includes/plugin.php using a standard text editor
2) Immediately after the opening line <?php add the following:
error_reporting(0);
@ini_set(‘display_errors’, 0);
3) Save and re-upload plugin.php to wp-admin/includes/
