Thanks for finding that. It's a bug and an oversight in the software that we somehow dropped that gamma file from recent versions of Lighthouse Studio. We'll fix it in the next release.
If you need that .gamma file, please zip up your Lighthouse Studio project (but do not include the Graphics folder in your zip, as it contains files that will be rejected by email filters) and send it to firstname.lastname@example.org.
Sorry for the inconvenience.