Show name and email for deleted poll officer's user account

Avoid to raise an exception `Module::DelegationError' when trying to
show the name and/or email of a poll officer whose user account has
been deleted.
We'll show a message "User deleted" and "Email deleted" instead.

config/locales/en/general.yml

@@ -724,6 +724,7 @@ en:
       to: "To"
     author_info:
       author_deleted: User deleted
+      email_deleted: Email deleted
     back: Go back
     check: Select
     check_all: All

config/locales/es/general.yml

@@ -722,6 +722,7 @@ es:
       to: "Hasta"
     author_info:
       author_deleted: Usuario eliminado
+      email_deleted: Email eliminado
     back: Volver
     check: Seleccionar
     check_all: Todos