Issue
https://gist.github.com/DPxKnightxZero/574be97efb54d586f662a1b5abc5b436

Seems to be a case of "item name typo on JSON file". Although, that shouldn't trigger on world generation, should only trigger when the entity in question (a Anti-Spider) is killed and attempts to drop the incorrectly referenced item.

Glad I could help you squash it :)