Removes invalid attributes from gravatar img tag.

git-svn-id: http://svn.redmine.org/redmine/trunk@16372 e93f8b46-1217-0410-a6f0-8f06a7374b81

lib/plugins/gravatar/lib/gravatar.rb

@@ -56,7 +56,7 @@ module GravatarHelper
       # double the size for hires displays
       options[:srcset] = "#{gravatar_url(email, options.merge(size: options[:size].to_i * 2))} 2x"
 
-      image_tag src, options
+      image_tag src, options.except(:rating, :size, :default, :ssl)
     end
     
     # Returns the base Gravatar URL for the given email hash