FrozenError: can't modify frozen String: ""

https://sentry.gitlab.net/gitlab/gitlabcom/issues/3308966/?referrer=gitlab_plugin

Gitlab::Email::UserNotAuthorizedError: Gitlab::Email::UserNotAuthorizedError
  lib/gitlab/email/handler/reply_processing.rb:81:in `validate_permission!'
    raise UserNotAuthorizedError unless author.can?(permission, try(:noteable) || project)
  lib/gitlab/email/handler/create_issue_handler.rb:37:in `execute'
    validate_permission!(:create_issue)
  lib/gitlab/email/receiver.rb:24:in `execute'
    handler.execute.tap do
  app/workers/email_receiver_worker.rb:33:in `execute_receiver'
    receiver.execute
  app/workers/email_receiver_worker.rb:23:in `perform'
    execute_receiver
...
(91 additional frame(s) were not displayed)

FrozenError: can't modify frozen String: ""
  config/initializers/mail_encoding_patch.rb:62:in `force_encoding'
    decoded = decoded.force_encoding(charset)
  config/initializers/mail_encoding_patch.rb:62:in `encoded'
    decoded = decoded.force_encoding(charset)
  config/initializers/mail_encoding_patch.rb:80:in `encoded'
    buffer << body.encoded(content_transfer_encoding, charset)
  lib/gitlab/email/failure_handler.rb:39:in `handle'
    EmailRejectionMailer.rejection(reason, receiver.mail.encoded, can_retry).deliver_later
  app/workers/email_receiver_worker.rb:93:in `handle_failure'
    Gitlab::Email::FailureHandler.handle(receiver, error)
...
(94 additional frame(s) were not displayed)

can't modify frozen String: ""