war crashes when game.save.json is 0 bytes

When trying to run war or warupd, it'll cash with an error in line 135 of warcommon.js

As a workaround, change into the worlds directory and then look in each subdir for a 0 length game.save.json file and delete it. Run the game again and it should work.

Documenting this both as a fix and a workaround.