Fix regression in dependency cycle check

[LaurentRDC]

This PR fixes #907, which triggered a corner case of the dependency cycle checking.

This patch was tested on the issue author's test case here: https://github.com/jtojnar/repro/tree/main/hakyll-poc-messed-cycle

@jtojnar Can you confirm that with this patch, you can compile your full site?

[jtojnar]

Can confirm it fixes my issue.

[Minoru]

Thanks!

I got curious what produces a CompilerRequire [] c result. Apparently it's this line: content/en/index.html or content/cs/index.html don't have a "destination" version, so a pattern returns no results, and thus this line uses an empty ids list.