Check if scrollTo target is a valid DOM element

[SteelWagstaff]

Description

We use a scrollTo function on Aldine which produces an error if the # target is not present (see below).

pressbooks-aldine/assets/scripts/routes/common.js

Lines 19 to 25 in 2b9ef72

	if ( document.location.hash && document.location.hash !== '#' ) {
	let anchorUponArrival = document.location.hash;
	setTimeout( function () {
	$( anchorUponArrival ).scrollTo( { duration: 1500 } );
	$( anchorUponArrival ).focus();
	}, 100 );
	}

Sentry Issue: PRESSBOOKS-7D

TypeError: t(...).scrollTo is not a function
  at None (/app/themes/pressbooks-aldine/dist/scripts/aldine.js:2:122430)
  at r (/app/plugins/pressbooks/assets/dist/scripts/sentry.js:2:80044)

Steps to Reproduce

1. Visit the network home page for a Pressbooks network and append a #string to the URL which does not correspond to an existing id on the page.
2. Open the console to see the scrollTo JS error.

aldine_JS_error.mp4

To fix: could check if target exists before attempting to scrollTo or could replace with vanilla JS scrollTo behaviour (https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollTo).