Empty quotes get added to class attribute in "Limit allowed HTML tags"

When you add 'class' as an allowed attribute in Basic HTML and save, it changes to class=""

Steps to reproduce:

1. Edit the Basic HTML filter
2. Add class to the allowed attributes of a tags
3. Save
4. class is changed to class=""

Screenshot of input before save:

Screenshot after save:

I note that the filter still works; I can still use the class attribute on a tags.

Original summary
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Hi, sorry, my english is not perfect. Be indulgent.

After a fresh install of Drupal 8.0.5, i try to add some attributes to "a" html tags (title, class, id, rel, target) . This works, but for class attributes, it's save with additionnal string ="" (see attachment). It's added in Basic HTML text format. I do the same with Restricted HTML and it's ok.