Fix undefined variable for copying empty folders

lib/files/view.php

@@ -467,7 +467,7 @@ class View {
 					}
 				} else {
 					if ($this->is_dir($path1) && ($dh = $this->opendir($path1))) {
-						$this->mkdir($path2);
+						$result = $this->mkdir($path2);
 						while ($file = readdir($dh)) {
 							if (!Filesystem::isIgnoredDir($file)) {
 								$result = $this->copy($path1 . '/' . $file, $path2 . '/' . $file);

tests/lib/files/view.php

@@ -235,9 +235,12 @@ class View extends \PHPUnit_Framework_TestCase {
 		\OC\Files\Filesystem::mount($storage2, array(), '/substorage');
 
 		$rootView = new \OC\Files\View('');
+		$rootView->mkdir('substorage/emptyfolder');
 		$rootView->copy('substorage', 'anotherfolder');
 		$this->assertTrue($rootView->is_dir('/anotherfolder'));
 		$this->assertTrue($rootView->is_dir('/substorage'));
+		$this->assertTrue($rootView->is_dir('/anotherfolder/emptyfolder'));
+		$this->assertTrue($rootView->is_dir('/substorage/emptyfolder'));
 		$this->assertTrue($rootView->file_exists('/anotherfolder/foo.txt'));
 		$this->assertTrue($rootView->file_exists('/anotherfolder/foo.png'));
 		$this->assertTrue($rootView->file_exists('/anotherfolder/folder/bar.txt'));