From 73c1b28ec731af4f017e59073905d30c72c79614 Mon Sep 17 00:00:00 2001
From: Jonathan Desrosiers <desrosj@git.wordpress.org>
Date: Tue, 9 Feb 2021 14:54:48 +0000
Subject: [PATCH] Twenty Twenty-One: Prevent Dark Mode related JavaScript
 error.

This prevents an `Uncaught TypeError` in the block editor when scrolling caused by the absence of a `#dark-mode-toggler` element.

Props ocean90, mukesh27, justinahinon.
Fixes #52473.

git-svn-id: https://develop.svn.wordpress.org/trunk@50269 602fd350-edb4-49c9-b593-d223f7449a82
---
 .../twentytwentyone/assets/js/dark-mode-toggler.js  | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/wp-content/themes/twentytwentyone/assets/js/dark-mode-toggler.js b/src/wp-content/themes/twentytwentyone/assets/js/dark-mode-toggler.js
index 22f5e3e15f..f5519d06e4 100644
--- a/src/wp-content/themes/twentytwentyone/assets/js/dark-mode-toggler.js
+++ b/src/wp-content/themes/twentytwentyone/assets/js/dark-mode-toggler.js
@@ -44,7 +44,9 @@ function darkModeInitialLoad() {
 }
 
 function darkModeRepositionTogglerOnScroll() {
-	var prevScroll = window.scrollY || document.documentElement.scrollTop,
+
+	var toggler = document.getElementById( 'dark-mode-toggler' ),
+		prevScroll = window.scrollY || document.documentElement.scrollTop,
 		currentScroll,
 
 		checkScroll = function() {
@@ -53,13 +55,16 @@ function darkModeRepositionTogglerOnScroll() {
 				currentScroll + ( window.innerHeight * 1.5 ) > document.body.clientHeight ||
 				currentScroll < prevScroll
 			) {
-				document.getElementById( 'dark-mode-toggler' ).classList.remove( 'hide' );
+				toggler.classList.remove( 'hide' );
 			} else if ( currentScroll > prevScroll && 250 < currentScroll ) {
-				document.getElementById( 'dark-mode-toggler' ).classList.add( 'hide' );
+				toggler.classList.add( 'hide' );
 			}
 			prevScroll = currentScroll;
 		};
-	window.addEventListener( 'scroll', checkScroll );
+
+	if ( toggler ) {
+		window.addEventListener( 'scroll', checkScroll );
+	}
 }
 
 darkModeInitialLoad();