From 30d6b30fecad92078a114396dd23f9294ee27b24 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 26 Aug 2024 16:39:54 +0530
Subject: [PATCH] E-book viewer: Fix a harmless error when the book contains
 page list references whose targets do not exist. Fixes #2077871 [Error when
 changing chapters](https://bugs.launchpad.net/calibre/+bug/2077871)

---
 src/pyj/read_book/anchor_visibility.pyj | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/pyj/read_book/anchor_visibility.pyj b/src/pyj/read_book/anchor_visibility.pyj
index 5c30ec1003..f97cf501ea 100644
--- a/src/pyj/read_book/anchor_visibility.pyj
+++ b/src/pyj/read_book/anchor_visibility.pyj
@@ -24,7 +24,7 @@ def ensure_anchor_cache_valid():
 def ensure_page_list_target_is_displayed(elem):
     # The stupid EPUB 3 examples have page list links pointing to
     # display:none divs. Sigh.
-    if window.getComputedStyle(elem).display is 'none':
+    if elem and window.getComputedStyle(elem).display is 'none':
         elem.textContent = ''
         elem.setAttribute('style', 'all: revert')