I got this crash when I was exploring my world with the newest version of Realistic Ore Veins. It seems to be due to be an incompatibility with Vampirism. Here's the report: https://paste.dimdev.org/ixajivibug.mccrash

Hmm. That is very strange. I blame Vampirism for not having a world provider. Either way I really shouldn't be checking the provider there. It might be fixed in 2.0.1