dev#209900 : no git on boogie

Storm_FileSystem_Volatile : check EntryAt return if null
so that it doesnot break

src/Storm/FileSystem/Volatile.php

@@ -204,6 +204,9 @@ class Storm_FileSystem_Volatile extends Storm_FileSystem_Abstract {
 
 
   public function fileNamesAt($path) {
+    if (!$this->entryAt($path))
+      return [];
+
     $collection = $this->entryAt($path)
                        ->select(fn($entry) => $entry->isFile());