Added check to handle when there is no data.

Author: Myztiq

lib/modem.js

@@ -264,7 +264,9 @@ Modem.prototype.demuxStream = function(stream, stdout, stderr) {
   var nextDataLength = null;
   var buffer = new Buffer('');
   function processData(data) {
-    buffer = Buffer.concat([buffer, data]);
+    if (data) {
+      buffer = Buffer.concat([buffer, data]);
+    }
     if (!nextDataType) {
       if (buffer.length >= 8) {
         var header = bufferSlice(8);