message: fix: defend against undefined XMLHttpRequest in _makeRequest
diff: @@ -1798,7 +1798,8 @@ Raven.prototype = {
  },
  _makeRequest: function(opts) {
  - var request = new XMLHttpRequest();
  + var request = _window.XMLHttpRequest && new _window.XMLHttpRequest();
  + if (!request) return;
  // if browser doesn't support CORS (e.g. IE7), we are out of luck
  var hasCORS = 'withCredentials' in request || typeof XDomainRequest !== 'undefined';
  