Board Thread:Support Requests - Getting Technical/@comment-27358554-20170714171647

I am trying to add a message above the Recirculation rail using JavaScript. I am using. The issue is, it doesn't work. In the console, I am getting this error: Uncaught TypeError: Cannot read property 'insertBefore' of null

Any ideas as of why this is and how I can fix it? Or maybe a different way of doing this? 