I can look at it, but aren't you being pretty unorthodox doing something via the API that's clearly not allowed through the UI?
This happens when processing Mirage variants. These are secondary album objects that appear on a "parent's" slide page; they don't have their own slide page.
In the published version of Mirage, there is a huge amount of code that generates variants.
I have realized that I can eliminate most of this code by hiding variants in init.bsh; jAlbum then generates the variants and their thumbnails. This technique works well.
I've never been a Mirage user, and at least at the present, I can't even try it (a simple, all-defaults test album crashes instantly, with just a couple of images). So, take this with a grain of salt....
jAlbum handles hidden folders very well. Everything in them gets processed, just as if those objects weren't hidden at all. Could Mirage keep variants in hidden folders, rather than having the skin "hide" variant objects proactively?
Yes, Mirage crashes in recent versions of jAlbum. I will release a repaired version soon. I am actually working on the repaired version and a complete rewrite simultaneously.
I don't think it would be practical to put variants in hidden folders; it would not be a good user interface.
jAlbum seems to handle hidden album objects of all types very well. I have just spotted this one problem, which seems like it should be a simple fix. As I said, I have a workaround, so it is not a show stopper.