When your site is automatically updated it takes all the changes we have made between one deploy and another. If you only modify the CSS of the site it will hardly break (more likely a part could stop working because some element has been refactored/changed etc), if you modify the templates or use JS scripts it is easier that something can break when we change something.
While we always try to be as forward-thinking as possible when making major changes that can impact hosted and self-hosted sites by creating dedicated topics in the #feature:announcements category, minor changes are only listed on Github until the new beta is released.
You could fix your code easily as @lucasbasquerotto said, but we have no way to warn you in advance of any changes we make or to warn you before deploying to the site.