Error moving to room controller

[super_aardvark]

I suddenly started getting the following stack trace, with no changes to my code or situation:

TypeError: Cannot read property 'undefined' of undefined
    at Grid.setWalkableAt (/opt/PathFinding.js/src/core/Grid.js:117:18)
    at Room.findPath (/opt/engine/dist/game/rooms.js:619:12)
    at RoomPosition.findPathTo (/opt/engine/dist/game/rooms.js:810:19)
    at Creep.moveTo (/opt/engine/dist/game/creeps.js:147:25)
    at module.exports (upgrader:23:23)
    at main:23:13

Line 23 of my 'upgrader' module is this:

            creep.moveTo(creep.room.controller);

[ir0x539]

confirmed

[PapaMufflon]

everything is kaputt

[Djinni]

Yeah, everything seems to have stopped in all rooms.

[ir0x539]

back to normal

[Hazmatic]

This appears to be broken for me in Simulation Mode.