From daf2be0f256ad45985a3f1be4f36349ed82149c4 Mon Sep 17 00:00:00 2001
From: bashonly <bashonly@protonmail.com>
Date: Wed, 30 Apr 2025 01:18:30 -0500
Subject: [PATCH] safer `_extract_chapters`

Authored by: bashonly
---
 yt_dlp/extractor/zdf.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/yt_dlp/extractor/zdf.py b/yt_dlp/extractor/zdf.py
index 4138db3216..36d4e5c2c7 100644
--- a/yt_dlp/extractor/zdf.py
+++ b/yt_dlp/extractor/zdf.py
@@ -56,10 +56,10 @@ class ZDFBaseIE(InfoExtractor):
         return int(mobj.group('width')) / int(mobj.group('height')) if mobj else None
 
     def _extract_chapters(self, data):
-        return traverse_obj(data, (lambda _, v: 'anchorOffset' in v, {
+        return traverse_obj(data, (lambda _, v: isinstance(v['anchorOffset'], (int, float)), {
             'start_time': ('anchorOffset', {float_or_none}),
             'title': ('anchorLabel', {str}),
-        }), default=None)
+        })) or None
 
     @staticmethod
     def _extract_subtitles(src):