Show error notice on visiting invalid page

[danieldegroot2]

What feature would you like to see added?

Show an error notice and/or (suggest) redirect to main home page on visiting an invalid url, for example https://osmcha.org/abc (or: https://osmcha.org/changeset/169422601 (without plural s) instead of https://osmcha.org/changesets/169422601 )

additionally above example could have a redirect applied or autofix suggestion provided. (but this is low priority)

Currently, the page loads fine, but the right side is empty.

Why would this be useful to you or other users?

Allow users to more easily see why page is empty and navigate to a valid url from an invalid url.

Currently, the user might be confused / think it is not loading properly.