Ticking Crash

When I open Minecraft in 18w21a both the launcher and Minecraft java crash after a few seconds. I have attached my bug report.

Description: Exception ticking world

java.lang.NullPointerException: Exception ticking world
	at bwi.a(SourceFile:186)
	at bwi.a(SourceFile:92)
	at bwm.d(SourceFile:60)
	at brt.a(SourceFile:298)
	at sj.a(SourceFile:307)
	at sk.a(SourceFile:249)
	at bbo.a(SourceFile:144)
	at sk.i_(SourceFile:199)
	at net.minecraft.server.MinecraftServer.w(SourceFile:694)
	at net.minecraft.server.MinecraftServer.v(SourceFile:627)
	at dii.v(SourceFile:156)
	at net.minecraft.server.MinecraftServer.run(SourceFile:532)
	at java.lang.Thread.run(Thread.java:745)