Bug 32575: Add an empty text body to fix multipart/mixed handling

By adding an empty text body, we force Email::Stuffer/Email::MIME
to use multipart/mixed handling for the attachment instead of forcing
a single part (ie direct attachment) email, which is not consistently
handled by different email clients.

An empty text body is language-neutral (ie not imposing English),
and it allows SMTP servers to inject organisational footers into
the email (e.g. confidentiality notices).

Signed-off-by: Magnus Enger <magnus@libriotech.no>
I have tested this solution in production, and it works for me.

Bug 32575: Tidy patch

Signed-off-by: Magnus Enger <magnus@libriotech.no>

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit 3e1d8b0628)
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>

misc/cronjobs/gather_print_notices.pl

@@ -291,9 +291,10 @@ sub send_files {
 
     my $email = Koha::Email->create(
         {
-            from    => $from,
-            to      => $to,
-            subject => 'Print notices for ' . $today_syspref,
+            from      => $from,
+            to        => $to,
+            subject   => 'Print notices for ' . $today_syspref,
+            text_body => ' ',
         }
     );