Uncaught TypeError: Cannot read property 'classList' of null

[yuryshulaev]

At some point it starts logging "Uncaught TypeError: Cannot read property 'classList' of null" and it becomes impossible to complete the turn. Sometimes it shows hideMoves and dropPiece in log:

Uncaught TypeError: Cannot read property 'classList' of null scripts.min.js:1
hideMoves
dropPiece

Here I wasn’t able to move the black king:

Chrome 23.0.1271.95 @ Windows 7

[BCleveland]

7 years too late but we actually found the issue #9 . Chess.js returns some strange data sometimes, which causes the valid moves to not be functional either when it happens.