Crash during Game System Conversion

[Merion]

After my 5 year long campaign ended recently, with the mad fire god defeated, I finally decided to convert my ancient legacy realm to a pathfinder one (game systems weren't implemented when I started). I tried once before, but ran into an error concerning tags, so I postponed as I was busy entering and preparing stuff for my weekly games.

Now with some free time I tried again and after the conversion process got stuck at 99% for like an hour, I got a weird exception (see screenshot). I couldn't even send the error report, as the error report window went unresponsive.

Anyone seen something like this before? Or knows about the utility.cpp file? I can't find it to check what line 690 says.