Should be completely fixed now, ping me if it isn't.
Do note that older browsers (such as Pale Moon and Waterfox) are considered unsupported. In this case, fixing the code was quick enough (and affected enough other browsers) that there was no reason not to, but be aware that things can and...
@TheMadPirate Right you're hitting the case where we haven't added the polyfill yet. Also we don't actually run grafana on the main site, so I'm not sure where you heard that from.
Change is intentional. We have it set to keep 100 images, so at roughly 1MB per image you can expect this to eat about 100MB. If this is too much for you, we can do some tuning as we update.