Uncaught exception on empty POST request

[WillyKaze]

firenodejs crash when an empty POST request is received:

HTTP    : POST /firestep <= {}
TTY     : WRITE(4) {}\n
TTY     : READ(4) {"s":-118} \n
HTTP    : firenodejs UNCAUGHT EXCEPTION:TypeError: Cannot read property 'id' of undefined
/home/fpd/repos/firenodejs/js/server.js:588
    throw error;
    ^

TypeError: Cannot read property 'id' of undefined
    at FireStepPlanner.onResponse (/home/fpd/repos/firenodejs/js/firestep/planner.js:365:26)
    at Object.response (/home/fpd/repos/firenodejs/js/firestep/planner.js:27:18)
    at FireStepDriver.onSerialData (/home/fpd/repos/firenodejs/js/firestep/driver.js:244:27)
    at Socket.<anonymous> (/home/fpd/repos/firenodejs/js/firestep/driver.js:83:26)
    at emitOne (events.js:90:13)
    at Socket.emit (events.js:182:7)
    at readableAddChunk (_stream_readable.js:147:16)
    at Socket.Readable.push (_stream_readable.js:111:10)
    at Pipe.onread (net.js:523:20)