Fix touching an invalid parent record for belongs_to

[exviva]

If the parent of a belongs_to record fails to be saved due to
validation errors, touch will be called on a new record, which causes
an exception (see #9320).

Example:

class Owner < ActiveRecord::Base
  validates_presence_of :name
end

class Pet < ActiveRecord::Base
  belongs_to :owner, touch: true
end

pet = Pet.new(owner: Owner.new)

# Before, this line would raise ActiveRecord::ActiveRecordError
# "can not touch on a new record object"
pet.save

[rafaelfranca]

Could you add a CHANGELOG entry?

[frodsan]

Before:

$ rails c
Loading development environment (Rails 4.0.0.beta1)
>> Pet.new(owner: Owner.new).save
ActiveRecord::ActiveRecordError: can not touch on a new record object

After:

$ rails c
Loading development environment (Rails 4.0.0.beta1)
>> Pet.new(owner: Owner.new).save
# => true

👍

[exviva]

@rafaelfranca done

[rafaelfranca]

needs a rebase

[exviva]

ugh...done @rafaelfranca :)

[rafaelfranca]

Thank you