Fix file transfer

lib/dataconnection.js

@@ -82,6 +82,7 @@ DataConnection.prototype._configureDataChannel = function() {
 
 DataConnection.prototype._cleanup = function() {
   if (this._dc && this._dc.readyState !== 'closed') {
+    console.log('closing', this._dc);
     this._dc.close();
     this._dc = null;
   }