[MC-219906] Minecraft crashes when spectating an entity submerged in water

The bug

When in spectator, you can right click entities to go into the entity and see from the entity's perspective. When right clicking an entity to spectate it underwater, you may see the perspective for a second, and then the client crashes. This is repeatable and consistent.

Stack trace

21w11a: crash-2021-03-17_14.52.43-client.txt

Description: Unexpected error

java.lang.ClassCastException: bdn cannot be cast to ejb
	at ejy.a(SourceFile:200)
	at eke.a(SourceFile:1130)
	at ejz.a(SourceFile:949)
	at ejz.a(SourceFile:767)
	at dsp.e(SourceFile:1073)
	at dsp.e(SourceFile:700)
	at net.minecraft.client.main.Main.main(SourceFile:216)