Uncaught TypeError: Cannot read property 'removeEventListener' of null

[mmcnl]

First of all, thanks so much @justinfagnani for the great work on this project (and of course on lit-html & LitElement)!

I've been using the chess-board component along with chess.js and in general it's been working wonderfully. However I'm sporadically getting errors like the following:

chessboard-element.ts:1405 Uncaught TypeError: Cannot read property 'removeEventListener' of null
    at HTMLDivElement.transitionComplete (chessboard-element.ts:1405)

Unfortunately so far I've not been able to deduce a pattern (other than this happens when my parent component renders) and so cannot yet provide reliable steps to reproduce. Here's the markup for the chess-board element in my parent component's render function:

          <chess-board
            @drag-start="${this.dragStart}"
            @drop="${this.drop}"
            draggable-pieces
            .orientation=${this.orientation}
            style="width: 80%"
            drop-off-board="snapback"
            position="${this.fen}"
          >
          </chess-board>

Is there anything I'm obviously doing wrong or perhaps do you have any troubleshooting tips? Thanks much!

[mmcnl]

Update: here's another js error I received:

Uncaught (in promise) TypeError: Cannot read property 'addEventListener' of null
    at chessboard-element.ts:1428
    at new Promise (<anonymous>)
    at HTMLElement._dropDraggedPieceOnSquare (chessboard-element.ts:1403)
    at async HTMLElement._stopDraggedPiece (chessboard-element.ts:1577)

[justinfagnani]

Hmm... seems like a race condition. I bet the animated piece is sometimes being removed from the DOM before the animation listener is cleaned up. I can take a look in a couple of days.

Thanks for the kind words!