For crates without a documentation key in their Cargo.toml, crates.io is supposed to generate a Documentation link to docs.rs. However, this Documentation link is sometimes missing on search results.

Steps to reproduce:

1. Open a fresh browser instance. (For example, I'm using chromium --user-data-dir="$(mktemp -d)" on Arch Linux.)
2. Navigate to https://crates.io/search?q=ndarray-npy
3. Observe that there is no Documentation link for the ndarray-npy crate. (It should be there, but it is missing. That's what this issue is about.)
4. Click on the ndarray-npy crate link (URL: https://crates.io/crates/ndarray-npy).
5. Click the "back" button on your browser to navigate back to the previous page.
6. Observe that the Documentation link has now appeared.

I'm observing this behavior for crates that do not include a documentation key in their Cargo.toml. Currently, examples of this include the ndarray-npy, py_literal, aho-corasick, unreachable, and void crates, among many others.