Crash game on start instead of not applying mod

[Grantapher]

@misterjoshua I thought chests were only affected if you tried to open them, did simply starting the world affect the chest contents?

A player logged in during this timeframe, opened chests, and this was the result. The one who logged in didn't realize this incompatibility had occurred because they weren't watching the game log, and the server was happy to admit them.

They also lost the bottom 2 rows of their character inventory, but they were able to restore cloud saves so this wasn't a huge problem.

Originally posted by @misterjoshua in #91 (comment)

[Grantapher]

This probably is worth doing. That or at least a much bigger warning on the main menu.