When I open Minecraft everything seems to work properly but when I join a world, it say's joining world than saving world and after saving world, it completely crashes Minecraft. After that it gives a crash message that says (The game crashed whilst unexpected error
Error: java.lang.NullPointerException: Cannot invoke "net.minecraft.class_746.method_5854()" because "player" is null)

Send the crash report. Seems like an issue with CBC not being updated to support Create 0.5.1.j yet though

Closing since no crash report