Fixed #23384 -- Allowed overriding part of a dictionary-type setting

This change is needed for upcoming changes where settings might be
grouped in a parent dictionary.
Do we have a formal authorization from the author to include this?

I don't see any license information in the post (which I just skimmed) and the footer says "Copyright © 2013 Ross McFarland. All Rights Reserved" which I don't believe is compatible with our license.