TypeError: Cannot read property 'error' of null

[huan]

v0.11.11

TypeError: Cannot read property 'error' of null
  File "/app/node_modules/wechaty/dist/src/puppet-web/bridge.js", line 645, in xml2js_1.parseString
    if (!obj.error) {
  File "/app/node_modules/xml2js/lib/parser.js", line 303, in Parser.<anonymous>
    return cb(null, result);
  File "events.js", line 96, in emitOne
  File "events.js", line 191, in Parser.emit
  File "/app/node_modules/xml2js/lib/parser.js", line 313, in Parser.exports.Parser.Parser.parseString
    this.emit("end", null);
...
(12 additional frame(s) were not displayed)

TypeError: Cannot read property 'error' of null