message: fix: use safe _window and _navigator references
  use _window.history instead of history (history is undefined in wechat miniapp environment)
  use _navigator.userAgent instead of navigator (navigator is undefined in wechat miniapp environment)
diff: @@ -1448,8 +1448,8 @@ Raven.prototype = {
  var hasPushAndReplaceState =
  !isChromePackagedApp &&
  _window.history &&
  - history.pushState &&
  - history.replaceState;
  + _window.history.pushState &&
  + _window.history.replaceState;
  if (autoBreadcrumbs.location && hasPushAndReplaceState) {
  // TODO: remove onpopstate handler on uninstall()
  var oldOnPopState = _window.onpopstate;
  @@ -1478,8 +1478,8 @@ Raven.prototype = {
  };
  };
  - fill(history, 'pushState', historyReplacementFunction, wrappedBuiltIns);
  - fill(history, 'replaceState', historyReplacementFunction, wrappedBuiltIns);
  + fill(_window.history, 'pushState', historyReplacementFunction, wrappedBuiltIns);
  + fill(_window.history, 'replaceState', historyReplacementFunction, wrappedBuiltIns);
  }
  if (autoBreadcrumbs.console && 'console' in _window && console.log) {
  @@ -1769,7 +1769,7 @@ Raven.prototype = {
  if (this._hasNavigator && _navigator.userAgent) {
  httpData.headers = {
  - 'User-Agent': navigator.userAgent
  + 'User-Agent': _navigator.userAgent
  };
  }
  