Outside the Y bounds of 0-255, with tall world mods such as Cubic Chunks, deaths while carrying items has crashed with no chest spawned. Without items there is no crash, but also no chest (probably intended behavior). Using Forge 2611.

Crash log: https://pastebin.com/04zmnF4F
latest.log (crash is at the end): https://pastebin.com/wpuCK3Ny
fml-client-latest.log: https://pastebin.com/M9AefY1J

This is fixed in 1.12.2-1.1.0.0. I'll release it after I fix another bug I'm working on.