Uncaught SyntaxError: Unexpected end of JSON input

[fenghou1st]

I can login limedrop.org, but all actions have no responds.
I open the browser console, an error message is repeating every second:

{"func":"poll","args":[],"profile":"fenghou","session":"QRRPzL8d/NaoXIcmk+NaH0P8oOvTVNhqptJY51Wu22nA4ybmwcIbI13GZZc05b4GQepn41DASR2DEEgsHPbWcficU8PfPkOt3U1keskuANvp7cMeeO2nmGYxKGmunx+W"}
VM113:1 Uncaught SyntaxError: Unexpected end of JSON input
    at JSON.parse (<anonymous>)
    at index.js:85
    at D2Bot.js:18
    at D2Bot.js:7
    at Object.<anonymous> (D2Bot.js:26)
    at i (jquery-2.2.4.min.js:2)
    at Object.fireWith [as resolveWith] (jquery-2.2.4.min.js:2)
    at z (jquery-2.2.4.min.js:4)
    at XMLHttpRequest.<anonymous> (jquery-2.2.4.min.js:4)