ConcurrentModificationException when a player leaves an active raid

Description: Exception ticking world

java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextNode(HashMap.java:1442)
	at java.util.HashMap$KeyIterator.next(HashMap.java:1466)
	at java.util.Collections$UnmodifiableCollection$1.next(Collections.java:1042)
	at axf.y(SourceFile:259)
	at axf.o(SourceFile:389)
	at axh.a(SourceFile:72)
	at vi.a(SourceFile:325)
	at net.minecraft.server.MinecraftServer.b(SourceFile:824)
	at ui.b(SourceFile:343)
	at net.minecraft.server.MinecraftServer.a(SourceFile:763)
	at net.minecraft.server.MinecraftServer.run(SourceFile:631)
	at java.lang.Thread.run(Thread.java:748)


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

-- Head --
Thread: Server thread
Stacktrace:
	at java.util.HashMap$HashIterator.nextNode(HashMap.java:1442)
	at java.util.HashMap$KeyIterator.next(HashMap.java:1466)
	at java.util.Collections$UnmodifiableCollection$1.next(Collections.java:1042)
	at axf.y(SourceFile:259)
	at axf.o(SourceFile:389)
	at axh.a(SourceFile:72)
	at vi.a(SourceFile:325)

-- Affected level --
Details:
	All players: 3 total; [vj['_toto128'/1745276, l='world', x=2868.05, y=80.80, z=-3932.27], vj['Ketcuz'/1815250, l='world', x=2804.96, y=77.00, z=-3841.55], vj['WinkBlue'/1672178, l='world', x=2877.93, y=79.00, z=-3933.09]]
	Chunk stats: ServerChunkCache: 4435
	Level dimension: minecraft:overworld
	Level name: world
	Level seed: -6615885059026489375
	Level generator: ID 00 - default, ver 1. Features enabled: true
	Level generator options: {}
	Level spawn location: World: (0,69,0), Chunk: (at 0,4,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 96757759 game time, 26049762 day time
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 120214 (now: false), thunder time: 5569 (now: true)
	Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Stacktrace:
	at net.minecraft.server.MinecraftServer.b(SourceFile:824)
	at ui.b(SourceFile:343)
	at net.minecraft.server.MinecraftServer.a(SourceFile:763)
	at net.minecraft.server.MinecraftServer.run(SourceFile:631)
	at java.lang.Thread.run(Thread.java:748)