crash message from ethersheet

gistfile1.txt

 info  - transport end (socket end)
   debug - set close timeout for client 1556672142472291423
   debug - cleared close timeout for client 1556672142472291423
   debug - cleared heartbeat interval for client 1556672142472291423

node.js:201
        throw e; // process.nextTick error, or 'error' event on first tick
              ^
TypeError: Cannot read property 'sheet_id' of undefined
    at Socket.<anonymous> (/home/ethersheet/EtherSheet/lib/server.js:95:32)
    at Socket.$emit (events.js:67:17)
    at Socket.onDisconnect (/home/ethersheet/EtherSheet/node_modules/socket.io/lib/socket.js:153:10)
    at SocketNamespace.handleDisconnect (/home/ethersheet/EtherSheet/node_modules/socket.io/lib/namespace.js:229:46)
    at Manager.onClientDisconnect (/home/ethersheet/EtherSheet/node_modules/socket.io/lib/manager.js:481:27)
    at WebSocket.end (/home/ethersheet/EtherSheet/node_modules/socket.io/lib/transport.js:467:20)
    at WebSocket.onSocketEnd (/home/ethersheet/EtherSheet/node_modules/socket.io/lib/transport.js:147:8)
    at CleartextStream.emit (events.js:64:17)
    at Array.1 (tls.js:790:22)
    at EventEmitter._tickCallback (node.js:192:41)