Broken image links

On the http://doc.qt.io/Qt-5/qtquickextras-dashboard-example.html page there is a broken image link with that is shown as a placeholder in Safari: http://doc.qt.io/Qt-5/images/qtquickextras-example-dashboard.png:

I can only see this "broken" placeholder in Safari, other browsers (Chrome, Firefox) don't show it, but the element is there:

And it's not only on this page, there are other docs pages like this.