Does not try to set attributes on initialization if provided argument…

… is nil

lib/virtus/instance_methods.rb

@@ -12,7 +12,7 @@ module InstanceMethods
     #
     # @api private
     def initialize(attribute_values = {})
-      self.attributes = attribute_values
+      self.attributes = attribute_values if attribute_values
     end
 
     # Returns a value of the attribute with the given name

spec/unit/virtus/instance_methods/initialize_spec.rb

@@ -0,0 +1,32 @@
+require 'spec_helper'
+
+describe Virtus::InstanceMethods, '#initialize' do
+  let(:described_class) do
+    Class.new do
+      include Virtus
+      attribute :name, String
+    end
+  end
+
+  let(:subject) do
+    described_class.new(attributes)
+  end
+
+  context "with valid argument" do
+    let(:attributes) do
+      {:name => 'john'}
+    end
+
+    it 'sets attributes' do
+      subject.name.should == attributes[:name]
+    end
+  end
+
+  context "with nil argument" do
+    let(:attributes) { nil }
+
+    it 'does not try to set attributes' do
+      expect { subject }.to_not raise_error(NoMethodError)
+    end
+  end
+end