[patch] When an attribute is an empty string, do not try and parse (and get current time)

* Spec to support handling empty strings when attribute is set to time.

lib/fog/core/attributes.rb

@@ -51,7 +51,7 @@ module Fog
         when :time
           class_eval <<-EOS, __FILE__, __LINE__
             def #{name}=(new_#{name})
-              if new_#{name}.nil? || new_#{name}.is_a?(Time)
+              if new_#{name}.nil? || new_#{name} == "" || new_#{name}.is_a?(Time)
                 @#{name} = new_#{name}
               else
                 @#{name} = Time.parse(new_#{name})

spec/core/attributes_spec.rb

@@ -2,6 +2,7 @@ require File.dirname(__FILE__) + '/../spec_helper'
 
 class FogAttributeTestModel < Fog::Model
   attribute :key_id, :aliases => "key", :squash => "id"
+  attribute :time, :type => :time
 end
 
 describe 'Fog::Attributes' do
@@ -23,6 +24,29 @@ describe 'Fog::Attributes' do
       end
     end
 
+    describe "when merging a time field" do
+      it "should accept nil as a suitable setting" do
+        data = {"time" => nil}
+        model = FogAttributeTestModel.new
+        model.merge_attributes(data)
+        model.time.should be_nil
+      end
+
+      it "should accept empty string as a suitable setting" do
+        data = {"time" => ""}
+        model = FogAttributeTestModel.new
+        model.merge_attributes(data)
+        model.time.should == ""
+      end
+
+      it "should parse strings to get a Datetime" do
+        test_time = Time.parse("2010-11-12T13:14:15")
+        data = {"time" => test_time.to_s}
+        model = FogAttributeTestModel.new
+        model.merge_attributes(data)
+        model.time.should == test_time
+      end
+    end
   end
 
 end