zonegrouptopology json parsing error

[daragallagher]

I think this change has occurred with a recent Sonos firmware update as I had also been using scripts to interact with the speaker http which broke recently while parsing the topology json.

TypeError: Cannot read property 'ZoneGroup' of undefined
at parseXML (/home/pi/sonos/denysvitali/sonos-web/server.js:850:59)
at Parser. (/home/pi/sonos/denysvitali/sonos-web/node_modules/xml2js/lib/parser.js:303:18)
at Parser.emit (events.js:189:13)
at SAXParser.onclosetag (/home/pi/sonos/denysvitali/sonos-web/node_modules/xml2js/lib/parser.js:261:26)
at emit (/home/pi/sonos/denysvitali/sonos-web/node_modules/sax/lib/sax.js:624:35)
at emitNode (/home/pi/sonos/denysvitali/sonos-web/node_modules/sax/lib/sax.js:629:5)
at closeTag (/home/pi/sonos/denysvitali/sonos-web/node_modules/sax/lib/sax.js:889:7)
at SAXParser.write (/home/pi/sonos/denysvitali/sonos-web/node_modules/sax/lib/sax.js:1436:13)
at Parser.exports.Parser.Parser.parseString (/home/pi/sonos/denysvitali/sonos-web/node_modules/xml2js/lib/parser.js:322:31)
at Parser.parseString (/home/pi/sonos/denysvitali/sonos-web/node_modules/xml2js/lib/parser.js:5:59)
at exports.parseString (/home/pi/sonos/denysvitali/sonos-web/node_modules/xml2js/lib/parser.js:354:19)
at Listener.listener.on (/home/pi/sonos/denysvitali/sonos-web/server.js:845:21)
at Listener.emit (events.js:189:13)
at Listener. (/home/pi/sonos/denysvitali/sonos-web/node_modules/sonos/lib/events/listener.js:63:12)
at Parser. (/home/pi/sonos/denysvitali/sonos-web/node_modules/xml2js/lib/parser.js:303:18)
at Parser.emit (events.js:189:13)
at SAXParser.onclosetag (/home/pi/sonos/denysvitali/sonos-web/node_modules/xml2js/lib/parser.js:261:26)
at emit (/home/pi/sonos/denysvitali/sonos-web/node_modules/sax/lib/sax.js:624:35)
at emitNode (/home/pi/sonos/denysvitali/sonos-web/node_modules/sax/lib/sax.js:629:5)
at closeTag (/home/pi/sonos/denysvitali/sonos-web/node_modules/sax/lib/sax.js:889:7)
at SAXParser.write (/home/pi/sonos/denysvitali/sonos-web/node_modules/sax/lib/sax.js:1436:13)
at Parser.exports.Parser.Parser.parseString (/home/pi/sonos/denysvitali/sonos-web/node_modules/xml2js/lib/parser.js:322:31)