It doesn't happen every time but I was able to hit it a second time. This time, soon after connecting, again, during maximising the window. Wonder if there is a race condition between mouse movement and the window being resized, perhaps. Could it be that getWidgetUnderMouse has stale window size ...

I can confirm, same stack trace. Ubuntu 16.04, Factorio 0.16.3. Crash occurs when client has almost finished connecting to server.

While the map was loading, I maximised the window. The window appeared to freeze for a bit, and then disappeared, and the below was in the crash log.

78.758 Info ...