Recent update has introduced a Javascript error that breaks site features

After a recent update, I’ve noticed we started getting the below error on every page load.

TypeError: Cannot read properties of null (reading ‘addEventListener’)
at window.onload (callout.js:26:60)

By itself, it’s not a huge deal, but if you try to concat / minify Javascript with something like WP Rocket, this error can cause the rest of the JS in the load path to not load properly.

The issue on admin/js/callout.js is that this block fails if there’s no element by that ID on the page:

document.getElementById("toplevel_page_sb-instagram-feed").addEventListener("mouseenter", (event) => {
			if (!document.body.classList.contains('index-php')) {
				positionCalloutContainer()
			}
		});

document.getElementById("toplevel_page_sb-instagram-feed").addEventListener("mouseleave", (event) => {
			if (!document.body.classList.contains('index-php')) {
				positionCalloutContainer(true)
			}

		});

I’ve temporarily solved this by putting a conditional around those blocks of:

if(document.getElementById("toplevel_page_sb-instagram-feed")){
...
}

This whole thing is odd to me, however, as it seems like this script shouldn’t even be loading on the front-end of the website? This appears to be an admin-side script, no? Did a recent change accidentally make this script load on front-end as well?