Update:
  What this fixes was later assigned CVE-2023-45872
  https://lists.qt-project.org/pipermail/development/2023-October/044577.html

https://bugs.gentoo.org/915582
https://bugreports.qt.io/browse/QTBUG-117944
https://codereview.qt-project.org/c/qt/qtsvg/+/510692
https://github.com/qt/qtsvg/commit/effc44495a33babd4cf7a2044123f420e6b3da1c
From: Paul Olav Tvete <paul.tvete@qt.io>
Date: Tue, 10 Oct 2023 10:14:22 +0200
Subject: [PATCH] Fix nullptr dereference with invalid SVG
--- a/src/svg/qsvghandler.cpp
+++ b/src/svg/qsvghandler.cpp
@@ -3606,6 +3606,8 @@ void QSvgHandler::init()
 
 static bool detectCycles(const QSvgNode *node, QList<const QSvgUse *> active = {})
 {
+    if (Q_UNLIKELY(!node))
+        return false;
     switch (node->type()) {
     case QSvgNode::DOC:
     case QSvgNode::G:
