Crashes when you try to search in REI
https://gist.github.com/Saereth/a2f58ffa1257336dcebb484a978893d2

Why is REI adding a gem item to the tab page? Those are not added by me for this exact reason

I have no idea, want me to open an issue with them as well?

Perhaps. Arguably apoth shouldn't be crashing if an invalid item is looked at, but rei also shouldn't be adding it to the display

In terms of the game ending abnormally, I get a similar error when I mouse hover LegacyGem on REI when I install LegendaryTooltips and the game is forced to end. (This one did not output a crash log)
I hope this is of some help...

Error Log
https://gist.github.com/HalsekiRaika/957b52bb39eb001c71f9befedcbb6630

Mod List
https://gist.github.com/HalsekiRaika/6c98b56c0e594fb6e58a78be51b83868

fixed for 6.1.2 - though REI shouldn't be adding this item to the creative tab.