From e81bc5ce81c594e71379df1168fd99d4062cea4f Mon Sep 17 00:00:00 2001
From: Robin Sheat <robin@catalyst.net.nz>
Date: Wed, 20 Oct 2010 20:13:15 +1300
Subject: [PATCH] Bug 4305 - prevent errors when handling invalid ISBN13 values

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Galen Charlton <gmcharlt@gmail.com>
---
 C4/Koha.pm | 1 +
 1 file changed, 1 insertion(+)

diff --git a/C4/Koha.pm b/C4/Koha.pm
index ab9131a9fb..dc2bcfa83b 100644
--- a/C4/Koha.pm
+++ b/C4/Koha.pm
@@ -1330,6 +1330,7 @@ sub _isbn_cleanup ($) {
     my $isbn = Business::ISBN->new( shift );
     return undef unless $isbn;
     $isbn = $isbn->as_isbn10 if $isbn->type eq 'ISBN13';
+    return undef unless $isbn;
     $isbn = $isbn->as_string;
     $isbn =~ s/-//g;
     return $isbn;
-- 
2.39.5