Generates invalid HAR file for www.expressen.se

[soulgalore]

Hi @janodvarko ,
we been testing the HAR export trigger a lot now in the coming version of https://github.com/tobli/browsertime and it works really good for us. There are some small tweaks but I mean it's the same problems with the HAR/waterfall inside Firefox. See when we can find the time to send PRs for those.

However, I found something today when I tested http://www.expressen.se (it's a Swedish newspaper site): There are some fields that are missing/invalid:

I've just upgraded to FF 46, and I haven't seen this before (but it can of course be new content on the site).

The HAR file:
https://gist.github.com/soulgalore/4071417f75753c0155dd83be0b60a4de

Best
Peter