Fix the mimetype filter in OC_Share_Backend_File

apps/files_sharing/lib/share/file.php

@@ -72,12 +72,14 @@ class OC_Share_Backend_File implements OCP\Share_Backend_File_Dependent {
 			// Only 1 item should come through for this format call
 			return array('path' => $items[key($items)]['path'], 'permissions' => $items[key($items)]['permissions']);
 		} else if ($format == self::FORMAT_FILE_APP) {
-			if (isset($parameters['mimetype_filter'])) {
+			if (isset($parameters['mimetype_filter']) && $parameters['mimetype_filter']) {
 				$mimetype_filter = $parameters['mimetype_filter'];
 			}
 			$files = array();
 			foreach ($items as $item) {
-				if (isset($mimetype_filter) && strpos($item['mimetype'], $mimetype_filter) !== 0) {
+				if (isset($mimetype_filter)
+					&& strpos($item['mimetype'], $mimetype_filter) !== 0
+					&& $item['mimetype'] != 'httpd/unix-directory') {
 					continue;
 				}
 				$file = array();