[9.x] Fix FTP root config (#40939)

* Fix FTP root config

* Update src/Illuminate/Filesystem/FilesystemManager.php

Co-authored-by: Frank de Jonge <[email protected]>

Co-authored-by: Frank de Jonge <[email protected]>

Author: driesvints

src/Illuminate/Filesystem/FilesystemManager.php

@@ -192,6 +192,10 @@ public function createLocalDriver(array $config)
      */
     public function createFtpDriver(array $config)
     {
+        if (! isset($config['root'])) {
+            $config['root'] = '';
+        }
+
         $adapter = new FtpAdapter(FtpConnectionOptions::fromArray($config));
 
         return new FilesystemAdapter($this->createFlysystem($adapter, $config), $adapter, $config);