Return from ActiveRecord::Base#attributes= unless value is a hash [#4070 state:committed]

Signed-off-by: José Valim <jose.valim@gmail.com>

activerecord/lib/active_record/base.rb

@@ -1471,7 +1471,7 @@ MSG
       #   user.send(:attributes=, { :username => 'Phusion', :is_admin => true }, false)
       #   user.is_admin?  # => true
       def attributes=(new_attributes, guard_protected_attributes = true)
-        return if new_attributes.nil?
+        return unless new_attributes.is_a? Hash
         attributes = new_attributes.stringify_keys
 
         multi_parameter_attributes = []

activerecord/test/cases/base_test.rb

@@ -61,6 +61,13 @@ class BasicsTest < ActiveRecord::TestCase
     assert_equal(topics(:first).author_email_address, Topic.find(1).author_email_address)
   end
 
+  def test_set_attributes_without_hash
+    topic = Topic.new
+    assert_nothing_raised do
+      topic.attributes = ''
+    end
+  end
+
   def test_integers_as_nil
     test = AutoId.create('value' => '')
     assert_nil AutoId.find(test.id).value