:imagesdir: does not like multiple slashes

[debuglevel]

$ asciidoctor -v
Asciidoctor 2.0.18 [https://asciidoctor.org]
Runtime Environment (ruby 3.1.0p0 (2021-12-25 revision fb4df44d16) [x86_64-linux]) (lc:UTF-8 fs:UTF-8 in:UTF-8 ex:UTF-8)

In some edge-cases, :imagesdir: does not like two slashes:

// works
:imagesdir: ./project/X/../Administration/

// does not work
:imagesdir: ./project/X//../Administration/

// works
:imagesdir: ./project//Administration/

This is quite hard to debug, as bash has no problem with e.g. ls ./project/X//../Administration/

Furthermore, the WARNING is asciidoctor: WARNING: image to embed not found or not readable: /.../asciidoc_thing/project/X/Administration/myimage.png which is also weird and confusing :)