I randomly got this error while playing level 23 in 6x10 Standard (game version 1.2.1, system version 2.5.0):
Scripts/gameManager.lua:251: attempt to index a nil value (local 'prevPath')
stack traceback:
Scripts/gameManager.lua:251: in method 'moveOnNode'
Scripts/gameManager.lua:187: in method 'move'
Scripts/gridCursor.lua:92: in function <Scripts/gridCursor.lua:71>
[C]: in field 'update'
main.lua:101: in function <main.lua:99>
Seems to just be a one-off though, I tried again and no errors occurred.