Fix a potential frozen string error in app/mailers/notify.rb

Signed-off-by: Rémy Coutable <remy@rymai.me>

1 files changed, 2 insertions, 2 deletions

diff --git a/app/mailers/notify.rb b/app/mailers/notify.rb
index 88ad4c3e893..6d86b60c50c 100644
--- a/app/mailers/notify.rb
+++ b/app/mailers/notify.rb
@@ -128,7 +128,7 @@ class Notify < BaseMailer
         address.display_name = reply_display_name(model)
       end
 
-      fallback_reply_message_id = "<reply-#{reply_key}@#{Gitlab.config.gitlab.host}>".freeze
+      fallback_reply_message_id = "<reply-#{reply_key}@#{Gitlab.config.gitlab.host}>"
       headers['References'] ||= []
       headers['References'].unshift(fallback_reply_message_id)
 
@@ -178,7 +178,7 @@ class Notify < BaseMailer
 
     headers['X-GitLab-Discussion-ID'] = note.discussion.id if note.part_of_discussion?
 
-    headers[:subject]&.prepend('Re: ')
+    headers[:subject] = "Re: #{headers[:subject]}" if headers[:subject]
 
     mail_thread(model, headers)
   end