After some effort, we have resolved this nasty crash that could occur after creating a new world and then saving. Huge apologies to everyone that ran into this and lost their progress. We really try to release stable builds but this one slipped through the cracks in our haste to get this update out for the Automation Festival. Thank you to those that reported this issue and to my friend Wacko for helping solve this one.
We will continue working on patches but they will likely live in experimental for a bit first so that way we don't run into another situation like this one.