Fix sending signed-only messages over list
wrong number of arguments (given 0, expected 1..2)
/usr/lib/ruby/gems/2.3.0/gems/mail-gpg-0.2.6/lib/mail/gpg/mime_signed_message.rb:7:in `initialize'
/usr/lib/ruby/gems/2.3.0/gems/mail-2.6.4/lib/mail/message.rb:267:in `new'
/usr/lib/ruby/gems/2.3.0/gems/mail-2.6.4/lib/mail/message.rb:267:in `reply'
/home/paz/dev/s/schleuder3/lib/schleuder/mail/message.rb:81:in `reply_to_signer'