/summon minecraft:illager_beast ~ ~ ~ {Passengers:[{id:slime}]}

Description: Ticking entity

java.lang.ClassCastException: agr cannot be cast to aoj$d
	at aoj$c.e(SourceFile:530)
	at ahk.a(SourceFile:129)
	at afr.cO(SourceFile:646)
	at afq.k(SourceFile:1988)
	at afr.k(SourceFile:511)
	at afq.S_(SourceFile:1839)
	at afr.S_(SourceFile:288)
	at aoj.S_(SourceFile:133)
	at afh.aJ(SourceFile:1688)
	at afq.aJ(SourceFile:2129)
	at aza.a(SourceFile:1153)
	at tz.a(SourceFile:377)
	at aza.g(SourceFile:1136)
	at aza.a(SourceFile:1201)
	at tz.a(SourceFile:377)
	at aza.g(SourceFile:1136)
	at aza.n_(SourceFile:1018)
	at tz.n_(SourceFile:293)
	at net.minecraft.server.MinecraftServer.b(SourceFile:732)
	at net.minecraft.server.MinecraftServer.a(SourceFile:661)
	at djr.a(SourceFile:125)
	at net.minecraft.server.MinecraftServer.run(SourceFile:564)
	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: Client thread
Stacktrace:
	at aoj$c.e(SourceFile:530)
	at ahk.a(SourceFile:129)
	at afr.cO(SourceFile:646)
	at afq.k(SourceFile:1988)
	at afr.k(SourceFile:511)
	at afq.S_(SourceFile:1839)
	at afr.S_(SourceFile:288)
	at aoj.S_(SourceFile:133)
	at afh.aJ(SourceFile:1688)
	at afq.aJ(SourceFile:2129)
	at aza.a(SourceFile:1153)
	at tz.a(SourceFile:377)
	at aza.g(SourceFile:1136)
	at aza.a(SourceFile:1201)
	at tz.a(SourceFile:377)
	at aza.g(SourceFile:1136)

-- Entity being ticked --
Details:
	Entity Type: minecraft:illager_beast (anw)
	Entity ID: 8265757
	Entity Name: Illager Beast
	Entity's Exact location: 54.50, 5.50, -48.50
	Entity's Block location: World: (54,5,-49), Chunk: (at 6,0,15 in 3,-4; contains blocks 48,0,-64 to 63,255,-49), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
	Entity's Momentum: 0.00, -0.08, 0.00
	Entity's Passengers: [aoj['Slime'/8265758, l='New World', x=54.50, y=5.50, z=-48.50]]
	Entity's Vehicle: ~~ERROR~~ NullPointerException: null
Stacktrace:
	at aza.n_(SourceFile:1018)
	at tz.n_(SourceFile:293)