Ensure assign_attributes and update_attributes do not fail on nil, closes #478.

activerecord/lib/active_record/base.rb

@@ -1688,6 +1688,8 @@ MSG
       #   user.name       # => "Josh"
       #   user.is_admin?  # => true
       def assign_attributes(new_attributes, options = {})
+        return unless new_attributes
+
         attributes = new_attributes.stringify_keys
         role = options[:as] || :default
 

activerecord/test/cases/mass_assignment_security_test.rb

@@ -87,6 +87,10 @@ class MassAssignmentSecurityTest < ActiveRecord::TestCase
     end
   end
 
+  def test_mass_assigning_does_not_choke_on_nil
+    Firm.new.assign_attributes(nil)
+  end
+
   def test_assign_attributes_uses_default_role_when_no_role_is_provided
     p = LoosePerson.new
     p.assign_attributes(attributes_hash)

activerecord/test/cases/persistence_test.rb

@@ -336,6 +336,10 @@ class PersistencesTest < ActiveRecord::TestCase
     assert !Topic.find(1).approved?
   end
 
+  def test_update_attribute_does_not_choke_on_nil
+    assert Topic.find(1).update_attributes(nil)
+  end
+
   def test_update_attribute_for_readonly_attribute
     minivan = Minivan.find('m1')
     assert_raises(ActiveRecord::ActiveRecordError) { minivan.update_attribute(:color, 'black') }