Another attempt of fixing OOB Horses. Just remove them from the world instead of setting it dead.

nms-patches/EntityHorse.patch

@@ -1,5 +1,5 @@
---- ../work/decompile-8eb82bde//net/minecraft/server/EntityHorse.java	Sun Nov 30 00:00:30 2014
-+++ src/main/java/net/minecraft/server/EntityHorse.java	Sun Nov 30 00:00:14 2014
+--- ../work/decompile-8eb82bde//net/minecraft/server/EntityHorse.java	Sun Nov 30 18:01:41 2014
++++ src/main/java/net/minecraft/server/EntityHorse.java	Sun Nov 30 18:00:23 2014
 @@ -4,6 +4,8 @@
  import java.util.Iterator;
  import java.util.List;
@@ -85,13 +85,14 @@
              }
  
              if (!this.cw() && this.passenger == null && this.random.nextInt(300) == 0 && this.world.getType(new BlockPosition(MathHelper.floor(this.locX), MathHelper.floor(this.locY) - 1, MathHelper.floor(this.locZ))).getBlock() == Blocks.GRASS) {
-@@ -730,6 +746,13 @@
+@@ -730,6 +746,14 @@
      }
  
      public void s_() {
 +        // CraftBukkit start - Remove out of bounds horses, fixes an vanilla bug
 +        if ( this.locY < -600 ) {
-+            die();
++            world.removeEntity(this);
++            MinecraftServer.getLogger().warn("Removed oob horse. Prevented a crash for Horse @ " + this.locX + ", " + this.locY + ", " + this.locZ);
 +            return;
 +        }
 +        // CraftBukkit end
@@ -99,7 +100,7 @@
          super.s_();
          if (this.world.isStatic && this.datawatcher.a()) {
              this.datawatcher.e();
-@@ -949,6 +972,7 @@
+@@ -949,6 +973,7 @@
          nbttagcompound.setInt("Temper", this.getTemper());
          nbttagcompound.setBoolean("Tame", this.isTame());
          nbttagcompound.setString("OwnerUUID", this.getOwnerUUID());
@@ -107,7 +108,7 @@
          if (this.hasChest()) {
              NBTTagList nbttaglist = new NBTTagList();
  
-@@ -1001,6 +1025,12 @@
+@@ -1001,6 +1026,12 @@
              this.setOwnerUUID(s);
          }
  
@@ -120,7 +121,7 @@
          AttributeInstance attributeinstance = this.getAttributeMap().a("Speed");
  
          if (attributeinstance != null) {
-@@ -1166,18 +1196,25 @@
+@@ -1166,18 +1197,25 @@
  
      public void v(int i) {
          if (this.cE()) {