net: check close callback is function

PR-URL: https://github.com/iojs/io.js/pull/609
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Evan Lucas <evanlucas@me.com>

lib/net.js

@@ -1368,7 +1368,7 @@ Server.prototype.close = function(cb) {
     self._emitCloseIfDrained();
   }
 
-  if (cb) {
+  if (typeof cb === 'function') {
     if (!this._handle) {
       this.once('close', function() {
         cb(new Error('Not running'));

test/parallel/test-net-listen-close-server-callback-is-not-function.js

@@ -0,0 +1,20 @@
+var assert = require('assert');
+var common = require('../common');
+var net = require('net');
+
+var server = net.createServer(assert.fail);
+var closeEvents = 0;
+
+server.on('close', function() {
+  ++closeEvents;
+});
+
+server.listen(common.PORT, function() {
+  assert(false);
+});
+
+server.close('bad argument');
+
+process.on('exit', function() {
+  assert.equal(closeEvents, 1);
+});