setHeader issue with node 0.12 and io.js 1.3.0

data.md

This was changed in https://github.com/joyent/node/commit/979d0ca8 from @trevnorris, but it results in a crash on 0.12+, io.js 1.x+ whereas 0.10 was functional.

test.js

var http = require('http'); 

function go(biff) {
  var req = http.request({
    method: 'GET',
    hostname : 'www.iojs.org',
    port: 80,
    path: '/',
    headers: {
      'foo-bar-baz': biff
    }
  }, function(res) {
    console.dir(res);
  });

  req.on('error', function(err) {
    console.error(err);
  });
}

go();