I think I managed to fix your file. In info.nut, line 46 reads:
_12 = "FIRS3: All economies", });
But as there are no more entries after this last one, this should read:
_12 = "FIRS3: All economies"});
After packing all files up into a .tar again with 7-zip, the script seemingly works, i.e. it can be selected in the AI/Game Script Configuration and I can also select "FIRS3: All economies" in the script configuration.
I'm a complete noob with OpenTTD customization, hopefully I did this right.
I attached my fixed version of your archive.