fix: do not fail on empty # and #top fragments

[MichaIng]

The empty "#" and "#top" fragments are always valid without related HTML element. Browser will scroll to the top of the page. Hence lychee must not fail on those.

Fixed #1599

[MichaIng]

Went with the two == first, but lint suggests is_empty(). The two test runs show the currently inconsistent results:

1. https://github.com/lycheeverse/lychee/actions/runs/12665712696/job/35295837656
   #top in file.html succeeds, # in file.html and # + #top in file1.md fail.
2. https://github.com/lycheeverse/lychee/actions/runs/12665772582/job/35296001037
   # in file.html succeeds, #top in file.html and # + #top in file1.md fail.

On my local tests, randomly, at least one, up to all of those failed. Would be interesting to know where this inconsistency is coming from, as I would suggest the same fragment to succeed or fail every time the same way 🤔.

[thiru-appitap]

updated my findings, the resolution and test information in here

please let me know if this works.

[MichaIng]

Awesome, the embarrassingly missed empty/top fragment handling in case of existing cache entry was the solution 👍. The redundant map_or is unrelated to this PR.

[mre]

@MichaIng, sorry, I dropped the ball on that one. What's the current status on this?
I can see some lint issues, but they seem to be unrelated. Anything else or is this ready to be merged?

[MichaIng]

@mre
It is ready to go. The map_or redundancy annotation of clippy is unrelated and probably just due to a clippy update: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_map_or
So

.map_or(false, ...

to

.is_some_and(...

seems sane. But in a dedicated PR I suggest.

[mre]

@MichaIng, can you rebase on top of master? I just fixed the clippy lint issues (#1625). That should make the build green.

[mre]

Thanks to you both, @thiru-appitap and @MichaIng. 🎉