Merge pull request #19861 from owncloud/fix-streamed-download-of-subfolders-master

The full name has to be tested if it's a dir

lib/private/files.php

@@ -86,7 +86,7 @@ class OC_Files {
 
 			if (!is_array($files)) {
 				$filename = $dir . '/' . $files;
-				if (!$view->is_dir($files)) {
+				if (!$view->is_dir($filename)) {
 					self::getSingleFile($view, $dir, $files, $onlyHeader);
 					return;
 				}