The bug
The ender dragon makes its breath attack at the highest block of the portal. This can cause MC-88301, but also a crash when you just build a tower of blocks on the portal. Then the ender dragon tries to fly to the top of the power and probably because it unloads itself, the game crashes.
How to reproduce
Go to the end
Place a about 200 block high tower on top of the portal
Go to the ground
Wait until the ender dragon flies upwards to the highest point
Crash report
1.11.2\: [^crash-2017-06-04_15.26.26-server.txt]
Description: Ticking entity
java.lang.ArrayIndexOutOfBoundsException: 1
at bbd.f(SourceFile:74)
at yq.k(SourceFile:68)
at yq.j(SourceFile:63)
at yq.c(SourceFile:24)
at yb.n(SourceFile:246)
at sw.A_(SourceFile:1703)
at sx.A_(SourceFile:282)
at ajs.a(SourceFile:1517)
at lw.a(SourceFile:718)
at ajs.h(SourceFile:1495)
at ajs.k(SourceFile:1378)
at lw.k(SourceFile:551)
at net.minecraft.server.MinecraftServer.D(SourceFile:634)
at net.minecraft.server.MinecraftServer.C(SourceFile:562)
at cch.C(SourceFile:154)
at net.minecraft.server.MinecraftServer.run(SourceFile:466)
at java.lang.Thread.run(Thread.java:745)
Linked issues
is duplicated by 8
relates to 3
Attachments
Comments 21
Confirmed for 15w42a
Confirmed for 15w43a
Confirmed for 15w44a
Confirmed for 15w46a
confirmed for 1.14.2 pre relase 1
no resolved
reopenned

@@unknown, the crash appears to be fixed, but the dragon still flies to the highest point (which can be 0 or 255) in 1.14.2-pre2.
Should MC-88371 be about that and was only the crash fixed?
The crash is fixed but the dragon still flies up,
Can confirm.