I've replicated this crash... kind of. The error message is different (trying to access an index that's too big rather than a negative one), but it's the same idea:
In Hypixel Skyblock, go to the Deep Caverns area
Get to one of the lower levels - I replicated the crash in Slimehill and initially encountered it in Obsidian Sanctuary
Wait - I'm unsure of what actually triggers the crash, but it seems to happen around these areas
Reproduction Steps
Crash Report File
Crash report
Additional Information
Compiled from next branch at commit.