Twenty Twenty-One: Check if anchor exists before triggering in-page navigation.

This prevents JavaScript errors when using hash in URLs without matching them to any existing anchor in the page.

Props rixeo, sabernhardt, pbearne.
Fixes #53619.


git-svn-id: https://develop.svn.wordpress.org/trunk@52213 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-content/themes/twentytwentyone/assets/js/primary-navigation.js

@@ -180,7 +180,9 @@ function twentytwentyoneExpandSubMenu( el ) { // jshint ignore:line
 				// Wait 550 and scroll to the anchor.
 				setTimeout(function () {
 					var anchor = document.getElementById(event.target.hash.slice(1));
-					anchor.scrollIntoView();
+					if ( anchor ) {
+						anchor.scrollIntoView();
+					}
 				}, 550);
 			}
 		} );