tests: Allow lfs.attributes to be NULL when traversing FS

test/helpers.lua

@@ -30,6 +30,7 @@ local function glob(initial_path, re, exc_re)
       if ((not exc_re or not checked_path:match(exc_re))
           and e:sub(1, 1) ~= '.') then
         local attrs = lfs.attributes(full_path)
+        if attrs then
           local check_key = attrs.dev .. ':' .. tostring(attrs.ino)
           if not checked_files[check_key] then
             checked_files[check_key] = true
@@ -42,6 +43,7 @@ local function glob(initial_path, re, exc_re)
         end
       end
     end
+  end
   return ret
 end