Merge pull request #5470 from sandeepravi/warning_fixes

fixed - warning: instance variable @controller not initialized

actionpack/lib/action_controller/caching/sweeping.rb

@@ -54,6 +54,11 @@ def cache_sweeper(*sweepers)
       class Sweeper < ActiveRecord::Observer #:nodoc:
         attr_accessor :controller
 
+        def initialize(*args)
+          super
+          @controller = nil
+        end
+
         def before(controller)
           self.controller = controller
           callback(:before) if controller.perform_caching