When a nil param value arrives in place of an expected hash, return
:key => nil, not simply nil.

Prior:

(rdb:1) params
{"book"=>nil}
(rdb:1) params.permit(book: { genre: :type })
nil

Now:

(rdb:1) params
{"book"=>nil}
(rdb:1) params.permit(book: { genre: :type })
{"book"=>nil}
When a nil param value arrives in place of an expected hash, return
:key => nil, not simply nil.

Prior:

(rdb:1) params
{"book"=>nil}
(rdb:1) params.permit(book: { genre: :type })
nil

Now:

(rdb:1) params
{"book"=>nil}
(rdb:1) params.permit(book: { genre: :type })
{"book"=>nil}
Merge branch 'master' of github.com:bjhess/strong_parameters
Classic Ruby hash syntax for max compatibility.
update with changes from bjhess