Nodejs handle error

I'm new at NodeJS and i got always this same error :

/var/www/html/helpdesk/node_modules/ent/encode.js:8
        throw new TypeError('Expected a String');
        ^

TypeError: Expected a String
    at Object.encode (/var/www/html/helpdesk/node_modules/ent/encode.js:8:15)
    at Socket.<anonymous> (/var/www/html/helpdesk/apps.js:32:22)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:191:7)
    at /var/www/html/helpdesk/node_modules/socket.io/lib/socket.js:503:12
    at _combinedTickCallback (internal/process/next_tick.js:73:7)
    at process._tickCallback (internal/process/next_tick.js:104:9)
/var/www/html/helpdesk/node_modules/ent/encode.js:8
        throw new TypeError('Expected a String');
        ^

How to handle this?

via obidano