I'm not exactly sure how this happened, but I was spending maybe an hour or so in the tutorial, mainly trying to learn how downloading signals works, before deciding I was done. However, I was completely unable to quit out as opening the menu was disabled, much like how events will disable the menu from being opened. Not only that, but even exiting fullscreen because the mouse is locked in the window by default, I had to force the game closed in order to exit. Not sure if an event somehow started in the tutorial and caused me to get stuck or what, the only thing I can think of is that this happened sometime after I got a "game save: null" message.