When a drop-in (such as `advanced-cache.php`) contains a PHP error, additional PHP errors are caused when displaying the error protection screen because `load_default_textdomain()` and `WP_Error` are not yet available.
Though recovery mode is not supported for `mu-plugins` and drop-ins, fatal error protection is. This change ensures the error screen is displayed when a fatal error is encountered within a drop-in and not a white screen.
Props TimothyBlynJacobs, spacedmonkey, daxelrod.
Fixes#47265.
git-svn-id: https://develop.svn.wordpress.org/trunk@45311 602fd350-edb4-49c9-b593-d223f7449a82