Heh, that's a nasty bug, but it's fixed in repo now. I'll explain why it's nasty.
This bug comes up when a being has an OnAction hook, the player dies, there's a nuke waiting to go off, and the hook doesn't check to see if the game is still running first.
The issue is this: The being has 2 OnAction hooks that run one after the other: The AI hook, and the Being's own hook. Only 3 beings have such a hook defined at the being level -- Shambler, Lava Elemental, and Apostle.
If you die to one of these beings because of one of their attacks, the death occurs during the AI OnAction script. The bug happens if you have a nuke that has yet to go off (because the nuke will explode as part of the player dying), as this will end up killing the attacking being.
Then the error: The being will attempt to run it's being-level OnAction hook, and fail because at this point it doesn't exist anymore. Crash.
TL,DR: Your game will error out if you die to the attacks of a Shambler, Lava Elemental, or Apostle and there is an active nuke on the map.