Breeding animals without LoveCause set cause crash

The bug

The server crashes when animals which have no LoveCauseLeast and LoveCauseMost value set breed.

[^crash-2017-05-19_18.57.20-server.txt] (1.12-pre5)

Description: Ticking entity

java.lang.NullPointerException: Ticking entity
	at amr.b(SourceFile:2627)
	at zt.do(SourceFile:162)
	at wt.i(SourceFile:86)
	at wt.e(SourceFile:63)
	at xd.a(SourceFile:129)
	at vo.cy(SourceFile:641)
	at vn.n(SourceFile:1887)
	at vo.n(SourceFile:501)
	at vb.n(SourceFile:144)
	at zt.n(SourceFile:43)
	at aae.n(SourceFile:120)
	at vn.B_(SourceFile:1742)
	at vo.B_(SourceFile:281)
	at amr.a(SourceFile:1514)
	at om.a(SourceFile:714)
	at amr.h(SourceFile:1499)
	at amr.k(SourceFile:1382)
	at om.k(SourceFile:547)
	at net.minecraft.server.MinecraftServer.D(SourceFile:634)
	at net.minecraft.server.MinecraftServer.C(SourceFile:562)
	at cgx.C(SourceFile:154)
	at net.minecraft.server.MinecraftServer.run(SourceFile:466)
	at java.lang.Thread.run(Unknown Source)

How to reproduce

Warning: Every time you re-enter the world the animals will try to breed again. It is therefore recommended to try reproducing this in a seperate world.

Summon two animals with only InLove set

/summon sheep ~ ~ ~ {InLove:1000}