User attributes do no retain new sort order

[Mesuva]

User attributes on /dashboard/users/attributes don't appear to save a new sort order.

The attributes can be dragged and dropped, but the callback to actually do the save of the new order (/index.php/ccm/system/attribute/attribute_sort/user) triggers a 500 error. The error appears to be: 'Class "\Concrete\Controller\Backend\AttributeSort" does not exist.'

[aembler]

Fixed the user attributes sort – but it looks like generic attribute sort in sets is broken. Not sure how this happened.