1v91 HTTP server callback called twice

I have just got started using Espruino, it looks great, but I have come across a few issues. I don't know if it's my fault, but I have found that when I use the built in HTTP server the callback function is called twice. Once with the query parameters, and once (second time) with them nulled out. This

I am using using a compiler to generate my JS, so it's slightly awkward but still readable. Here is the callback used by wifi.connect()

 var onConnected = function onConnected(err) {
    if (err == null) {
      console.log("IP: " + wifi.getIP().ip);

      var http = require("http");

      var callback = function callback(request, response) {
        var query = void 0;
        var matchValue = url.parse(request.url, true).query;

        if (matchValue == null) {
          query = null;
        } else {
          query = matchValue;
        }

        response.writeHead(200);
        response.write("<a href=\"?led=1\">on</a><br/><a href=\"?led=0\">off</a>");
        response.end("sup dawg?");
        console.log("Callback called");

        if (query != null) {
          var matchValue_1 = query.led;

          if (matchValue_1 === "1") {
            digitalWrite(outPutPin, 1);
          } else {
            digitalWrite(outPutPin, 0);
          }
        }
      };

      var server = http.createServer(callback);
      server.listen(80);
    } else {
      console.log("Error: " + err);
    }
  };    

log output from hitting the page once:

=undefined
IP: 192.168.1.102
Callback called
Callback called

The work around I'm using is just to only set the LEDs if the query is not null. What might be going wrong?

Thanks