Initialize variables in a Redmine plugin (Issue Reminder)

I'm trying to add project name and query name in mails sent by a Redmine plugin because every mail subject is the same

The model of the email which is sent is here. The model of the mailer is here :

I tried to add

:subject => Setting.plugin_redmine_issue_reminder['issue_reminder_mail_subject'] || "<#{project.name}: #{query.name}>" ` in ` issue_reminder_mailer.rb ` 

but each time I try to test it with rake reminder:exec[test] RAILS_ENV="production" --trace , I get NameError: undefined local variable or method `project' for #

What's wrong and how can I solve it?