Browser Firefox version 74.0 (64-bit), Win10
Set your location settings for page https://reittiopas.hsl.fi/ to disallow
Should see index page with origin empty and destination set
Set origin to your location and accept location permission prompt and set "remember decision"
Should go to itinerary page properly
Should get page crash like attached image
With nice obfuscated error msg:
Could not reproduce this in Chrome or Edge, maybe something to do with location permissions?
Also can't reproduce on Firefox 68.6.0esr (64-bit) on Debian 10 VM