Entities causing ticking entity crash

Everytime i log onto my world entities start crashing my game and everytime i relog it just continues crashing.
Don't exactly know why entities are "ticking" but please fix this in the snapshot.
Crash info:

---- Minecraft Crash Report ----
// My bad.

Time: 3/14/18 3:37 PM
Description: Ticking entity

java.lang.ClassCastException: afn cannot be cast to afj
	at adb.a(SourceFile:41)
	at acz.a(SourceFile:22)
	at adl.a(SourceFile:94)
	at abw.cL(SourceFile:644)
	at abv.l(SourceFile:1895)
	at abw.l(SourceFile:504)
	at ajs.l(SourceFile:33)
	at aki.l(SourceFile:257)
	at abv.S_(SourceFile:1750)
	at abw.S_(SourceFile:284)
	at ajs.S_(SourceFile:38)
	at aki.S_(SourceFile:232)
	at ajg.S_(SourceFile:252)
	at aug.a(SourceFile:1617)
	at se.a(SourceFile:705)
	at aug.h(SourceFile:1593)
	at aug.p_(SourceFile:1475)
	at se.p_(SourceFile:538)
	at net.minecraft.server.MinecraftServer.w(SourceFile:702)
	at net.minecraft.server.MinecraftServer.v(SourceFile:627)
	at czd.v(SourceFile:155)
	at net.minecraft.server.MinecraftServer.run(SourceFile:532)
	at java.lang.Thread.run(Thread.java:745)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Thread: Server thread
Stacktrace:
	at adb.a(SourceFile:41)
	at acz.a(SourceFile:22)
	at adl.a(SourceFile:94)
	at abw.cL(SourceFile:644)
	at abv.l(SourceFile:1895)
	at abw.l(SourceFile:504)
	at ajs.l(SourceFile:33)
	at aki.l(SourceFile:257)
	at abv.S_(SourceFile:1750)
	at abw.S_(SourceFile:284)
	at ajs.S_(SourceFile:38)
	at aki.S_(SourceFile:232)
	at ajg.S_(SourceFile:252)
	at aug.a(SourceFile:1617)
	at se.a(SourceFile:705)
	at aug.h(SourceFile:1593)

-- Entity being ticked --
Details:
	Entity Type: minecraft:drowned (ajg)
	Entity ID: 302
	Entity Name: Drowned
	Entity's Exact location: 6818.70, 2.02, 48828.70
	Entity's Block location: World: (6818,2,48828), Chunk: (at 2,0,12 in 426,3051; contains blocks 6816,0,48816 to 6831,255,48831), Region: (13,95; contains chunks 416,3040 to 447,3071, blocks 6656,0,48640 to 7167,255,49151)
	Entity's Momentum: 0.19, 0.00, 0.19
	Entity's Passengers: []
	Entity's Vehicle: ~~ERROR~~ NullPointerException: null
Stacktrace:
	at aug.p_(SourceFile:1475)
	at se.p_(SourceFile:538)

-- Affected level --
Details:
	Level name: cool survival thing idk
	All players: 1 total; [sg['Oofchestra'/285, l='cool survival thing idk', x=6818.03, y=2.00, z=48825.83]]
	Chunk stats: ServerChunkCache: 850 Drop: 0
	Level seed: 4851134097974845496
	Level generator: ID 00 - default, ver 1. Features enabled: true
	Level generator options: 
	Level spawn location: World: (-148,64,-184), Chunk: (at 12,4,8 in -10,-12; contains blocks -160,0,-192 to -145,255,-177), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
	Level time: 2353377 game time, 38585 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 61063 (now: false), thunder time: 15077 (now: false)
	Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: true
Stacktrace:
	at net.minecraft.server.MinecraftServer.w(SourceFile:702)
	at net.minecraft.server.MinecraftServer.v(SourceFile:627)
	at czd.v(SourceFile:155)
	at net.minecraft.server.MinecraftServer.run(SourceFile:532)
	at java.lang.Thread.run(Thread.java:745)

-- System Details --
Details:
	Minecraft Version: 18w11a
	Operating System: Windows 10 (amd64) version 10.0
	Java Version: 1.8.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 107505448 bytes (102 MB) / 285212672 bytes (272 MB) up to 1073741824 bytes (1024 MB)
	JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=16M
	Profiler Position: N/A (disabled)
	Player Count: 1 / 8; [sg['Oofchestra'/285, l='cool survival thing idk', x=6818.03, y=2.00, z=48825.83]]
	Data Packs: vanilla, file/Vanilla Enhanced (incompatible)
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.*