debconf: add patches to safeguard Template.pm and Cache.pm

helpers/DATA/debconf/patch_changes/000-add_Template_undef_guard.patch

@@ -0,0 +1,12 @@
+diff --git a/Debconf/Template.pm b/Debconf/Template.pm
+index 9ab4833d..c3649929 100644
+--- a/Debconf/Template.pm
++++ b/Debconf/Template.pm
+@@ -140,6 +140,7 @@ Get an existing template (it may be pulled out of the database, etc).
+ sub get {
+ 	my Debconf::Template $this=shift;
+ 	my $template=shift;
++	return unless defined $template && length $template;
+ 	return $template{$template} if exists $template{$template};
+ 	if ($Debconf::Db::templates->exists($template)) {
+ 		$this = fields::new($this);

helpers/DATA/debconf/patch_changes/001-add_DbDriver_Cache_undef_guard.patch

@@ -0,0 +1,12 @@
+diff --git a/Debconf/DbDriver/Cache.pm b/Debconf/DbDriver/Cache.pm
+index 1b0e36fb..2e80d3bb 100644
+--- a/Debconf/DbDriver/Cache.pm
++++ b/Debconf/DbDriver/Cache.pm
+@@ -122,6 +122,7 @@ undef -- marked as deleted in the cache, so does not exist
+ sub exists {
+ 	my $this=shift;
+ 	my $item=shift;
++	return 0 unless defined $item && length $item;
+ 
+ 	return $this->{cache}->{$item}
+ 		if exists $this->{cache}->{$item};

helpers/make-debconf

@@ -0,0 +1,28 @@
+#!/bin/sh
+#
+#    Copyright (C) 2025  Luis Guzmán <ark@switnet.org>
+#
+#    This program is free software; you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License as published by
+#    the Free Software Foundation; either version 2 of the License, or
+#    (at your option) any later version.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program; if not, write to the Free Software
+#    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
+#
+
+VERSION=1
+
+. ./config
+
+apply_patch_changes
+
+changelog "Add undef guard for Template.pm and Cache.pm"
+
+package