The mystery deepens. Those lines are correct, and they're the only two changes in that entire template file from the previous version.
Give me a bit more time to mull it over - I'll probably need to send you a temporary replacement file that will spit out some variable values to the system console. The error message frustratingly doesn't actually tell me which variable is void.
ETA: Just one thing - when you look at the file, are you actually seeing the "%20" encodings in line 36? When you simply look at the file, you should be seeing spaces where those are, like this:
Mystery solved!! I just grabbed the lifeboat file from your website (oh, thank you David for making that the default). There, sitting in the image directory of the album, is infopage.htt. And, it's the version from Saturn 11. So, when you make the album, jAlbum says, "I'm supposed to use the infopage.htt template file. But this user has provided his own, so I'll try to process that one." Poof - error!
There should be no template files in the image directory. Open your jAlbum project. Choose Tools, Open directories, Image directory. Delete infopage.htt from that location. Now, Saturn v.12 will work properly.
You may not like one of the changes, however - I've eliminated the now rather dated-looking PNG navigation icons, and am using only SVG's.
While waiting for your reply I looked at the project on my hard drive and the infopage.htt file was dated sometime in 2017. So I deleted it from my hard drive and copied the new infopage.htt file from the skin directory to the project. All is good now.
So I ... copied the new infopage.htt file from the skin directory to the project.
NO!! Do not do that. The template files, like infopage.htt, should never be sitting in the project. They should exist only in the skin directory. By copying it to the project, you're just setting yourself up for the same kind of error the next time there's a skin update.
Open the project (image) directory, and deleteinfopage.htt.