Avoid calling is_missing on LoadErrors. Closes #7460.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@7644 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/CHANGELOG

 *SVN*
 
+* Avoid calling is_missing on LoadErrors. Closes #7460. [ntalbott]
+
 * Move Railties' Dispatcher to ActionController::Dispatcher, introduce before_ and after_dispatch callbacks, and warm up to non-CGI requests.  [Jeremy Kemper]
 
 * The tag helper may bypass escaping.  [Jeremy Kemper]

actionpack/lib/action_controller/helpers.rb

@@ -173,7 +173,7 @@ def default_helper_module!
           module_path = module_name.split('::').map { |m| m.underscore }.join('/')
           require_dependency module_path
           helper module_name.constantize
-        rescue LoadError => e
+        rescue MissingSourceFile => e
           raise unless e.is_missing? module_path
           logger.debug("#{name}: missing default helper path #{module_path}") if logger
         rescue NameError => e