Add patch from upstream merge request: compatibility with newer libxml2.

Thanks: Paul Gevers for the bug report.
Closes: #995132

debian/patches/libxml2_2.9.12.patch

+From d74d1f186b2e2c6334a78b895b0ea811a16617a4 Mon Sep 17 00:00:00 2001
+From: Emmanuel Seyman <emmanuel@seyman.fr>
+Date: Mon, 14 Jun 2021 21:12:07 +0200
+Subject: [PATCH] fallback to toString() when toStringC14N(1) gives an empty
+ string
+
+Bug: https://github.com/tokuhirom/HTML-TreeBuilder-LibXML/issues/16
+Bug-Debian: https://bugs.debian.org/995132
+
+---
+ lib/HTML/TreeBuilder/LibXML/Node.pm | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/lib/HTML/TreeBuilder/LibXML/Node.pm b/lib/HTML/TreeBuilder/LibXML/Node.pm
+index f3b4e81..b710dda 100644
+--- a/lib/HTML/TreeBuilder/LibXML/Node.pm
++++ b/lib/HTML/TreeBuilder/LibXML/Node.pm
+@@ -74,7 +74,8 @@ sub as_HTML {
+     {
+         local $@; # protect existing $@
+         my $output = eval { $_[0]->{node}->toStringC14N(1) };
+-        return $@ ? $_[0]->{node}->toString : $output;
++        return $_[0]->{node}->toString if ($@ or $output eq '');
++        return $output;
+     }
+ }
+ 

debian/patches/series

+libxml2_2.9.12.patch