wifi.ping() memory leak and undefined

can confirm that fix is working as expected

test snippet:

var Wifi = require("Wifi");
var i = 1;
var sleep = 7000;
setInterval(function(){
  console.log("run:",i++);
  Wifi.ping("192.168.194.1", function(rc){
    console.log("ping result",rc);
  });
  console.log("process.memory().free",process.memory().free);
},sleep);

output:

run: 1
process.memory().free 1524
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 20,
  "seqNo": 341, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 0,
  "seqNo": 0, "timeoutCount": 0, "bytes": 0, "error": -1 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 11,
  "seqNo": 343, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 3,
  "seqNo": 344, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 0,
  "seqNo": 0, "timeoutCount": 0, "bytes": 0, "error": -1 }
run: 2
process.memory().free 1524
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 0,
  "seqNo": 0, "timeoutCount": 0, "bytes": 0, "error": -1 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 0,
  "seqNo": 0, "timeoutCount": 0, "bytes": 0, "error": -1 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 27,
  "seqNo": 348, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 1,
  "seqNo": 349, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 1,
  "seqNo": 350, "timeoutCount": 0, "bytes": 32, "error": 0 }
run: 3
process.memory().free 1524
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 6,
  "seqNo": 351, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 1,
  "seqNo": 352, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 1,
  "seqNo": 353, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 4,
  "seqNo": 354, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 2,
  "seqNo": 355, "timeoutCount": 0, "bytes": 32, "error": 0 }
run: 4
process.memory().free 1524
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 5,
  "seqNo": 356, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 2,
  "seqNo": 357, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 2,
  "seqNo": 358, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 2,
  "seqNo": 359, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 1,
  "seqNo": 360, "timeoutCount": 0, "bytes": 32, "error": 0 }
run: 5
process.memory().free 1524
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 9,
  "seqNo": 361, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 3,
  "seqNo": 362, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 2,
  "seqNo": 363, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 3,
  "seqNo": 364, "timeoutCount": 0, "bytes": 32, "error": 0 }
ping result { "totalCount": 0, "totalBytes": 0, "totalTime": 0, "respTime": 2,
  "seqNo": 365, "timeoutCount": 0, "bytes": 32, "error": 0 }