make error_messages_for return "" for nil objects

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3438 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* allow nil objects for error_messages_for [Michael Koziarski]
+
 * Refactor human_size to exclude decimal place if it is zero. [Marcel Molina Jr.]
 
 * Update to Prototype 1.5.0_pre0 [Sam Stephenson]

actionpack/lib/action_view/helpers/active_record_helper.rb

@@ -103,7 +103,7 @@ module ActionView
       def error_messages_for(object_name, options = {})
         options = options.symbolize_keys
         object = instance_variable_get("@#{object_name}")
-        unless object.errors.empty?
+        if object && !object.errors.empty?
           content_tag("div",
             content_tag(
               options[:header_tag] || "h2",
@@ -113,6 +113,8 @@ module ActionView
             content_tag("ul", object.errors.full_messages.collect { |msg| content_tag("li", msg) }),
             "id" => options[:id] || "errorExplanation", "class" => options[:class] || "errorExplanation"
           )
+        else
+          ""
         end
       end
 

actionpack/test/template/active_record_helper_test.rb

@@ -119,6 +119,10 @@ class ActiveRecordHelperTest < Test::Unit::TestCase
     assert_dom_equal %(<div class="errorExplanation" id="errorExplanation"><h2>1 error prohibited this post from being saved</h2><p>There were problems with the following fields:</p><ul><li>Author name can't be empty</li></ul></div>), error_messages_for("post")
     assert_equal %(<div class="errorDeathByClass" id="errorDeathById"><h1>1 error prohibited this post from being saved</h1><p>There were problems with the following fields:</p><ul><li>Author name can't be empty</li></ul></div>), error_messages_for("post", :class => "errorDeathByClass", :id => "errorDeathById", :header_tag => "h1")
   end
+  
+  def test_error_messages_for_handles_nil
+    assert_equal "", error_messages_for("notthere")
+  end
 
   def test_form_with_string_multipart
     assert_dom_equal(