Make error_message_on handle nil objects. [dan]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@5799 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_view/helpers/active_record_helper.rb

@@ -85,8 +85,10 @@ module ActionView
       #   <%= error_message_on "post", "title", "Title simply ", " (or it won't work)", "inputError" %> =>
       #     <div class="inputError">Title simply can't be empty (or it won't work)</div>
       def error_message_on(object, method, prepend_text = "", append_text = "", css_class = "formError")
-        if errors = instance_variable_get("@#{object}").errors.on(method)
+        if object = instance_variable_get("@#{object}") && errors = object.errors.on(method)
           content_tag("div", "#{prepend_text}#{errors.is_a?(Array) ? errors.first : errors}#{append_text}", :class => css_class)
+        else 
+          ''
         end
       end
 

actionpack/test/template/active_record_helper_test.rb

@@ -170,6 +170,10 @@ class ActiveRecordHelperTest < Test::Unit::TestCase
   def test_error_messages_for_handles_nil
     assert_equal "", error_messages_for("notthere")
   end
+  
+  def test_error_message_on_handles_nil
+    assert_equal "", error_message_on("notthere", "notthere")
+  end
 
   def test_error_messages_for_many_objects
     assert_dom_equal %(<div class="errorExplanation" id="errorExplanation"><h2>2 errors 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><li>User email can't be empty</li></ul></div>), error_messages_for("post", "user")