child_process: make .send() throw if message is undefined

JSON.stringify(undefined) returns "undefined" but JSON.parse() doesn't know how
to parse that.

lib/child_process.js

@@ -111,7 +111,11 @@ function setupChannel(target, channel) {
   };
 
   target.send = function(message, sendHandle) {
-    if (!target._channel) throw new Error('channel closed');
+    if (typeof message === 'undefined') {
+      throw new TypeError('message cannot be undefined');
+    }
+
+    if (!target._channel) throw new Error("channel closed");
 
     // For overflow protection don't write if channel queue is too deep.
     if (channel.writeQueueSize > 1024 * 1024) {

test/simple/test-child-process-fork.js

@@ -35,6 +35,11 @@ n.on('message', function(m) {
   messageCount++;
 });
 
+// https://github.com/joyent/node/issues/2355 - JSON.stringify(undefined)
+// returns "undefined" but JSON.parse() cannot parse that...
+assert.throws(function() { n.send(undefined); }, TypeError);
+assert.throws(function() { n.send(); }, TypeError);
+
 n.send({ hello: 'world' });
 
 var childExitCode = -1;