Crash when open map after spawning a horse

---- Minecraft Crash Report ----
// Don't be sad. I'll do better next time, I promise!

Time: 19/05/13 14:28
Description: Rendering screen

java.lang.OutOfMemoryError: unable to create new native thread
	at java.lang.Thread.start0(Native Method)
	at java.lang.Thread.start(Unknown Source)
	at net.minecraft.server.MinecraftServer.u(SourceFile:581)
	at asm.a(SourceFile:1372)
	at aux.e(SourceFile:166)
	at auy.a(SourceFile:218)
	at auw.a(SourceFile:175)
	at aux.a(SourceFile:191)
	at bcz.b(SourceFile:707)
	at asm.O(SourceFile:611)
	at asm.c(SourceFile:544)
	at net.minecraft.client.main.Main.main(SourceFile:78)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
	at java.lang.Thread.start0(Native Method)
	at java.lang.Thread.start(Unknown Source)
	at net.minecraft.server.MinecraftServer.u(SourceFile:581)
	at asm.a(SourceFile:1372)
	at aux.e(SourceFile:166)
	at auy.a(SourceFile:218)
	at auw.a(SourceFile:175)
	at aux.a(SourceFile:191)

-- Screen render details --
Details:
	Screen name: bhz
	Mouse location: Scaled: (199, 53). Absolute: (398, 372)
	Screen size: Scaled: (427, 240). Absolute: (854, 480). Scale factor of 2
Stacktrace:
	at bcz.b(SourceFile:707)
	at asm.O(SourceFile:611)
	at asm.c(SourceFile:544)
	at net.minecraft.client.main.Main.main(SourceFile:78)

-- System Details --
Details:
	Minecraft Version: 13w19a
	Operating System: Windows 8 (x86) version 6.2
	Java Version: 1.7.0_21, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
	Memory: 221138168 bytes (210 MB) / 378134528 bytes (360 MB) up to 1037959168 bytes (989 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 9, tcache: 0, allocated: 1, tallocated: 63
	LWJGL: 2.9.0
	OpenGL: Intel(R) HD Graphics 4000 GL version 4.0.0 - Build 9.17.10.2843, Intel
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Texture Pack: Default
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: ~~ERROR~~ NullPointerException: null