As far as I can tell, this crash was caused by an iron golem fighting a "pyro creeper," which is a creeper that spawns with some additional effects that I can't find on any of V-Tweaks' pages.

Crash: https://pastebin.com/eaizQkMX
V-Tweaks issue: oitsjustjose/V-Tweaks#79 (comment)

Thanks for reporting this issue. I am not exactly sure how you created these conditions but it looks like something that wasn't a player attacked a pyro creeper while holding flint and steel. This issue should be resolved in the new update.