Remove a warning by making sure the renamed file is a dir before trying and opening it

lib/files/cache/scanner.php

@@ -94,7 +94,7 @@ class Scanner {
 		}
 
 		$size = 0;
-		if ($dh = $this->storage->opendir($path)) {
+		if ($this->storage->is_dir($path) && ($dh = $this->storage->opendir($path))) {
 			\OC_DB::beginTransaction();
 			while ($file = readdir($dh)) {
 				if ($file !== '.' and $file !== '..') {