made a small tweak

lib/Twig/Loader/Filesystem.php

@@ -111,7 +111,7 @@ class Twig_Loader_Filesystem implements Twig_LoaderInterface
         $this->validateName($name);
 
         foreach ($this->paths as $path) {
-            if (file_exists($path.'/'.$name) && !is_dir($path.'/'.$name)) {
+            if (is_file($path.'/'.$name)) {
                 return $this->cache[$name] = $path.'/'.$name;
             }
         }