Correct how base options for missing config files are preloaded

Author: u01jmg3

src/Illuminate/Foundation/Bootstrap/LoadConfiguration.php

@@ -5,6 +5,7 @@
 use Illuminate\Config\Repository;
 use Illuminate\Contracts\Config\Repository as RepositoryContract;
 use Illuminate\Contracts\Foundation\Application;
+use Illuminate\Support\Collection;
 use SplFileInfo;
 use Symfony\Component\Finder\Finder;
 
@@ -69,7 +70,7 @@ protected function loadConfigurationFiles(Application $app, RepositoryContract $
             ? $this->getBaseConfiguration()
             : [];
 
-        foreach (array_diff(array_keys($base), array_keys($files)) as $name => $config) {
+        foreach (Collection::make($base)->diffKeys($files) as $name => $config) {
             $repository->set($name, $config);
         }