Fix Docker::Image.create when m is nil

Sometime when pulling for second time the API responds
with nil somewhere, leading to:

       undefined method `[]' for nil:NilClass
     # /var/lib/gems/2.1.0/gems/docker-api-1.13.7/lib/docker/image.rb:102:in `create'

lib/docker/image.rb

@@ -99,7 +99,7 @@ def create(opts = {}, creds = nil, conn = Docker.connection)
       headers = !credentials.nil? && Docker::Util.build_auth_header(credentials)
       headers ||= {}
       body = conn.post('/images/create', opts, :headers => headers)
-      id = Docker::Util.fix_json(body).select { |m| m['id'] }.last['id']
+      id = Docker::Util.fix_json(body).reverse.find { |m| m && m.has_key?('id') }.fetch('id')
       new(conn, 'id' => id, :headers => headers)
     end