Map and charts don't render with tracking protection enabled in browser

[peter-]

With Firefox's Enhanced Tracking Protection enabled MET's start page shows a big empty space where the map of covered federations would otherwise appear (whatever one thinks of the usefulness of such maps):

Disabling tracking protection (effectively unblocking Google's gstatic.com) makes the map render properly:

The same effect can also be seen on the charts page for a given federation: no charts rendered with tracking protection enabled, charts rendered once tracking protection has been disabled.

It would be desirable to make MET usable without forcing its users to run their web browser with insecure settings.