来自 gstatic 的 PhantomJS JavaScript 错误，但浏览器中没有错误

我最近通过 PhantomJS 测试套件运行我们的网站，遇到了无法在浏览器中手动重现的 JavaScript 错误。这些错误是在 Google 地图 api 中发现的，Capybara 返回的文本如下：

TypeError: Unable to delete property.
TypeError: Unable to delete property.
   at :215
   at https://maps.gstatic.com/maps-api-v3/api/js/19/3/main.js:20 in cf
   at https://maps.gstatic.com/maps-api-v3/api/js/19/3/main.js:20 in cf
   at https://maps.gstatic.com/maps-api-v3/api/js/19/3/main.js:19
   at :214
   at https://maps.gstatic.com/maps-api-v3/api/js/19/3/main.js:20 in cf
   at https://maps.gstatic.com/maps-api-v3/api/js/19/3/main.js:20 in cf
   at https://maps.gstatic.com/maps-api-v3/api/js/19/3/main.js:21
   at :176
   at :31
   at https://maps.gstatic.com/maps-api-v3/api/js/19/3/main.js:26 in Yf
   at :178

这是 Capybara、PhantomJS 或 Google 地图 API 的已知错误吗？问题是否是由 PhantomJS 中的用户代理字符串引起的？

我正在使用 Cucumber / Poltergeist，并通过创建以下扩展来解决这个问题：

/features/support/env.rb

Capybara::Poltergeist::Driver.new(app, 
  :extensions => ["features/support/ignore_gmaps_errors.js"]
)

/features/support/ignore_gmaps_errors.js

window.onerror = function(message) {
  if (message == 'TypeError: Unable to delete property.') {
    console.log('Ignoring gmaps error');
    return false;
  } else {
    return true;
  }
};