[MC-90423] Ender Dragon makes breath attack at highest block placed in the center column of the portal

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)