"The requested version does not exist" for yanked crates

For situations where all the versions of a crate has been yanked you get the following error:

The requested version does not exist

when visiting the latest url:

• https://docs.rs/$YANKED_CRATE_NAME.
• https://docs.rs/$YANKED_CRATE_NAME/latest/.
• https://docs.rs/$YANKED_CRATE_NAME/latest/$YANKED_CRATE_NAME/index.html.

Generally when crate authors would share links to the documentation for their crate they would share a link to the generic "latest" page. This means all of those links are dead even though the author may have pushed a final version explaining an alternative crate to use, before yanking that version too.

Real life example:
https://docs.rs/constfft/latest/constfft/
https://docs.rs/constfft/0.2.4/constfft/index.html

Suggestion: redirect to the most recent docs, even when all the versions are yanked, but add a banner that no un-yanked versions exist anymore.