skip_parse does not work if property is nil

[denisovlev]

Option skip_parse on property is ignored when when corresponding value on input hash is nil.
Expected: when skip_parse: true representer does not try to set any value in represented model
Actual: representer tries to set value if value is nil

it 'representable skip_parse nil' do
  class TestRepresenter < Representable::Decorator
    include ::Representable::Hash
    property :property1
    property :property2, skip_parse: true
  end

  class TestModel
    attr_accessor :property1
    attr_reader :property2

    def initialize
      @property1 = '123'
      @property2 = '456'
    end
  end

  m = TestModel.new
  r = TestRepresenter.new(m)

  expected_hash = {property1: '123', property2: '456'}.stringify_keys
  expect(r.to_hash).to eq(expected_hash)

  new_hash = {property1: '789', property2: nil}.stringify_keys
  r.from_hash(new_hash) # << fails here when trying to set readonly property2
  expect(m.property1).to eq('789')
  expect(m.property2).to eq('456')
end