Minecraft crashed after my death. I can’t open my inventory, it kills me when I move and here is what this error appears:
https://gist.github.com/filipsowka/be301c1628a9264e8fb048ac806b62f6
I’ve got the newest sponge version and the newest forge.
OK, I managed to do this myself.
It was a problem with the TrashSlot mod.
When I deleted it, it’s fine. 
I believe this is still a bug with Sponge - you should be able to use that mod with Sponge without needing any changes. Can you post the exact version of the mod and Sponge?
Looks like these reports are on the same issue