Hopper: java.util.ConcurrentModificationException

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-3022405/

Crash:

java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.remove(HashMap.java:1443)
	at st.bO(SourceFile:515)
	at st.U(SourceFile:310)
	at sk.A_(SourceFile:351)
	at st.A_(SourceFile:1621)
	at aav.A_(SourceFile:271)
	at lx.k_(SourceFile:282)
	at mh.F_(SourceFile:179)
	at er.a(SourceFile:232)
	at mg.c(SourceFile:187)
	at net.minecraft.server.MinecraftServer.D(SourceFile:652)
	at net.minecraft.server.MinecraftServer.C(SourceFile:562)
	at ccb.C(SourceFile:154)
	at net.minecraft.server.MinecraftServer.run(SourceFile:466)
	at java.lang.Thread.run(Thread.java:745)

The following is the first clean report made public about this crash:

---- Minecraft Crash Report ----
// My bad.

Time: 30/09/16 17:43
Description: Ticking player

java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.remove(HashMap.java:1443)
	at st.bO(SourceFile:515)
	at st.U(SourceFile:310)
	at sk.A_(SourceFile:351)
	at st.A_(SourceFile:1621)
	at aav.A_(SourceFile:271)
	at lx.k_(SourceFile:282)
	at mh.F_(SourceFile:179)
	at er.a(SourceFile:232)
	at mg.c(SourceFile:187)
	at net.minecraft.server.MinecraftServer.D(SourceFile:652)
	at net.minecraft.server.MinecraftServer.C(SourceFile:562)
	at ccb.C(SourceFile:154)
	at net.minecraft.server.MinecraftServer.run(SourceFile:466)
	at java.lang.Thread.run(Thread.java:745)


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.remove(HashMap.java:1443)
	at st.bO(SourceFile:515)
	at st.U(SourceFile:310)
	at sk.A_(SourceFile:351)
	at st.A_(SourceFile:1621)
	at aav.A_(SourceFile:271)

-- Player being ticked --
Details:
	Entity Type: null (lx)
	Entity ID: 2005
	Entity Name: DivadNix
	Entity's Exact location: -13487,65, 61,00, -12353,81
	Entity's Block location: World: (-13488,61,-12354), Chunk: (at 0,3,14 in -843,-773; contains blocks -13488,0,-12368 to -13473,255,-12353), Region: (-27,-25; contains chunks -864,-800 to -833,-769, blocks -13824,0,-12800 to -13313,255,-12289)
	Entity's Momentum: 0,00, -0,02, 0,00
	Entity's Passengers: []
	Entity's Vehicle: ~~ERROR~~ NullPointerException: null
Stacktrace:
	at lx.k_(SourceFile:282)
	at mh.F_(SourceFile:179)
	at er.a(SourceFile:232)

-- Ticking connection --
Details:
	Connection: er@2aad0ec7
Stacktrace:
	at mg.c(SourceFile:187)
	at net.minecraft.server.MinecraftServer.D(SourceFile:652)
	at net.minecraft.server.MinecraftServer.C(SourceFile:562)
	at ccb.C(SourceFile:154)
	at net.minecraft.server.MinecraftServer.run(SourceFile:466)
	at java.lang.Thread.run(Thread.java:745)

-- System Details --
Details:
	Minecraft Version: 16w39c
	Operating System: Windows 10 (amd64) version 10.0
	Java Version: 1.8.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 533638600 bytes (508 MB) / 1060372480 bytes (1011 MB) up to 1060372480 bytes (1011 MB)
	JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
	IntCache: cache: 1, tcache: 1, allocated: 12, tallocated: 94
	Profiler Position: N/A (disabled)
	Player Count: 1 / 8; [lx['DivadNix'/2005, l='Mundo 1.11!!!', x=-13487,65, y=61,00, z=-12353,81]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-3022405/77408417/