Rails3: model: replace deprecated errors.add_to_base at save_issue_with_child_records of Issue

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@7589 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/issue.rb

@@ -634,7 +634,7 @@ class Issue < ActiveRecord::Base
           end
         rescue ActiveRecord::StaleObjectError
           attachments[:files].each(&:destroy)
-          errors.add_to_base l(:notice_locking_conflict)
+          errors.add :base, l(:notice_locking_conflict)
           raise ActiveRecord::Rollback
         end
       end