Attachment becomes body if no body specified

[ehuelsmann]

When using the following code:

    my $mail = Email::Stuffer
        ->from( 'me@example.com' )
        ->to(  'you5@example.com' )
        ->subject(  'Invoice 1' )
        ->text_body( $body,
                     encoding     => '8bit',
                     content_type => 'text/plain',
                     charset      => 'utf8' )
        ->header( 'Message-Id' => 'some-id@example.com' );

Where $body is undef, followed by:

        $mail->attach($att->{content},
                      content_type => $att->{mime_type},
                      disposition  => 'attachment',
                      filename     => $att->{file_name});

Results in:

Content-Transfer-Encoding: base64
Content-Type: application/pdf
Date: Sun, 21 Apr 2024 18:44:05 +0000
From: me@example.com
MIME-Version: 1.0
Message-Id: <17137250450.ab5e3.4060@lsmb>
Received: from localhost.localdomain by mailhog.example (MailHog)
          id 4C21yTDtN0a83oBQ64AuQsIPa6LQbd41eVeFpE3iG88=@mailhog.example; Sun, 21 Apr 2024 18:44:05 +0000
Return-Path: <me@example.com>
Subject: Invoice 1
To: you5@example.com

JVBERi0xLjUKJdDUxdgKMyAwIG9iago8PAovTGVuZ3RoIDEzMjUgICAgICAKL0ZpbHRlciAvRmxh
...
aYdWxwplbmRzdHJlYW0KZW5kb2JqCnN0YXJ0eHJlZgoyOTUzOAolJUVPRgo=

Meaning that the body of the mail now has become the attachment. I would have expected something along the lines of:

Content-Transfer-Encoding: 7bit
Content-Type: multipart/mixed; boundary=17137249691.Ab6AfaD9f.4055
Date: Sun, 21 Apr 2024 18:42:49 +0000
From: me@example.com
MIME-Version: 1.0
Message-Id: <17137249690.B89b16C.4055@lsmb>
Received: from localhost.localdomain by mailhog.example (MailHog)

          id ZamsOjJ0rDUJIu3gIDx45-C190giHpJV6oje6_3aaPA=@mailhog.example; Sun, 21 Apr 2024 18:42:49 +0000
Return-Path: <me@example.com>
Subject: Invoice 1
To: you4@example.com



--17137249691.Ab6AfaD9f.4055
Date: Sun, 21 Apr 2024 18:42:49 +0000
MIME-Version: 1.0
Content-Type: text/plain; charset=utf8
Content-Transfer-Encoding: 8bit

--17137249691.Ab6AfaD9f.4055
Date: Sun, 21 Apr 2024 18:42:49 +0000
MIME-Version: 1.0
Content-Type: application/pdf
Content-Disposition: attachment; filename=invoice-1.pdf
Content-Transfer-Encoding: base64

JVBERi0xLjUKJdDUxdgKMyAwIG9iago8PAovTGVuZ3RoIDEzMjUgICAgICAKL0ZpbHRlciAvRmxh
...
aYdWxwplbmRzdHJlYW0KZW5kb2JqCnN0YXJ0eHJlZgoyOTUzOAolJUVPRgo=

--17137249691.Ab6AfaD9f.4055--