Rails 3.2.11 --> Empty arrays being parsed as "nil" instead of empty array

gistfile1.md

Rails 3.2.10

Post JSON with nested attributes:

> RestClient.post "http://localhost:3000/users.json", {"users" => [] }.to_json, { 'Content-Type' => 'application/json'}

Dump params from controller:

{"users"=>[], "action"=>"create", "controller"=>"users", "format"=>"json"}

Note that "addresses" is an empty array

Rails 3.2.11

Post JSON with nested attributes:

> RestClient.post "http://localhost:3000/users.json", {"users" => [] }.to_json, { 'Content-Type' => 'application/json'}

Dump params from controller:

{"users"=>{}, "action"=>"create", "controller"=>"users", "format"=>"json"})

Note that "user" is no longer an empty array.

We've noticed that the change also affects nested attributes (the parsed value will be nil)