[BUGFIX] #53 Add missing FolderInterface namespace

Author: Joey Bouten

Classes/EventListener/Backend/DefaultUploadFolder.php

@@ -9,6 +9,7 @@
 use TYPO3\CMS\Core\Resource\Exception\FolderDoesNotExistException;
 use TYPO3\CMS\Core\Resource\Exception\InsufficientFolderAccessPermissionsException;
 use TYPO3\CMS\Core\Resource\Folder;
+use TYPO3\CMS\Core\Resource\FolderInterface;
 use TYPO3\CMS\Core\Resource\ResourceFactory;
 use TYPO3\CMS\Core\Utility\File\ExtendedFileUtility;
 use TYPO3\CMS\Core\Utility\GeneralUtility;