I have not had any problems playing in my world before (1.12.2), but today when trying to open it, it crashed my game, and the description was that there was an exception in server tick loop. I have even tried opening a copy of the world, but it still does not work.
Crash Report: https://cdn.discordapp.com/attachments/598202002690015312/605447973517787156/crash-2019-07-29_13.04.21-server.txt