From 08d7b56746a93c25db2991403fec7e56cbae132d Mon Sep 17 00:00:00 2001
From: m-holger <m-holger@kubitscheck.org>
Date: Tue, 11 Apr 2023 17:16:40 +0100
Subject: [PATCH] Prevent destruction of shared null objects

---
 libqpdf/QPDF.cc | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/libqpdf/QPDF.cc b/libqpdf/QPDF.cc
index 83944be..c7cc137 100644
--- a/libqpdf/QPDF.cc
+++ b/libqpdf/QPDF.cc
@@ -247,10 +247,11 @@ QPDF::~QPDF()
     // but we'll explicitly clear the xref table anyway just to
     // prevent any possibility of resolve() succeeding.
     this->m->xref_table.clear();
-    auto null_obj = QPDF_Null::create();
     for (auto const& iter: this->m->obj_cache) {
         iter.second.object->disconnect();
-        iter.second.object->destroy();
+        if (iter.second.object->getTypeCode() != ::ot_null) {
+            iter.second.object->destroy();
+        }
     }
 }
 
--
libgit2 0.21.4