I'm currently working on a customers multilingual website that has a language switch in the menu bar. On every blog article you can click that switch. However, some articles don't have a translations. So when you click on the link (the language button) you arrive at a 404-page claiming that the article doesn't exist.
Or in short: Oftentimes articles without a linked translated article link to a 404-page.
What would be the best practice to handle 404-pages caused by links to non-existing translations?
Edit: These are old articles that will not be translated, so that's not an option.