Merged r20923 from trunk to 4.2-stable (#34999).

git-svn-id: http://svn.redmine.org/redmine/branches/4.2-stable@20924 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/attachment.rb

@@ -370,7 +370,7 @@ class Attachment < ActiveRecord::Base
   def self.latest_attach(attachments, filename)
     return unless filename.valid_encoding?
 
-    attachments.sort_by(&:created_on).reverse.detect do |att|
+    attachments.sort_by{|attachment| [attachment.created_on, attachment.id]}.reverse.detect do |att|
       filename.casecmp?(att.filename)
     end
   end