Changing versions doesn't stay on same item

[jsha]

Steps to reproduce:

1. Visit https://docs.rs/rustls/latest/rustls/struct.ConfigBuilder.html
2. Click the crate name in the topbar to open the menu
3. Select a different version (e.g. 0.21.9)

Expected result:

Wind up on https://docs.rs/rustls/0.21.9/rustls/struct.ConfigBuilder.html, that is, the same page in a different version.

Actual result:

Wind up on https://docs.rs/rustls/0.21.9/rustls/index.html, the index page.

[syphar]

I can definitely reproduce this, and it's odd that this stopped working, I remember these parts are more thoroughly tested than others, but also both the rustdoc-redirect-handler & the rustdoc-page handler are relatively complex.

[syphar]

this is a regression coming from #2113, cc @GuillaumeGomez @Nemo157

I'll see if I can figure out the solution with my limited JS knowledge

[syphar]

it also switches back to the default target instead of keeping the currently selected target.