Ensure entity isn't destroyed when trying to show it. Fixes BUKKIT-2038

If two players (or a player and any other entity) are teleported to the
same location in the same tick they will both get added to the other's
destroy queue then have a new entity spawn packet sent. Next tick the
destroy queue will be processed and they will then be invisible to each
other. To prevent this situation we remove the entity from the destroy
queue when sending out a spawn packet for them.

src/main/java/net/minecraft/server/EntityTrackerEntry.java

@@ -234,12 +234,14 @@ public class EntityTrackerEntry {
             if (d0 >= (double) (-this.b) && d0 <= (double) this.b && d1 >= (double) (-this.b) && d1 <= (double) this.b) {
                 if (!this.trackedPlayers.contains(entityplayer) && this.d(entityplayer)) {
                     // CraftBukkit start
-                    if (tracker instanceof EntityPlayer) {
+                    if (this.tracker instanceof EntityPlayer) {
-                        Player player = ((EntityPlayer) tracker).getBukkitEntity();
+                        Player player = ((EntityPlayer) this.tracker).getBukkitEntity();
                         if (!entityplayer.getBukkitEntity().canSee(player)) {
                             return;
                         }
                     }
+
+                    entityplayer.g.remove(Integer.valueOf(this.tracker.id)); // Should be called destroyQueue
                     // CraftBukkit end
                     this.trackedPlayers.add(entityplayer);
                     Packet packet = this.b();

src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java

@@ -631,7 +631,6 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
         EntityTracker tracker = ((WorldServer) entity.world).tracker;
         EntityPlayer other = ((CraftPlayer) player).getHandle();
         EntityTrackerEntry entry = (EntityTrackerEntry) tracker.trackedEntities.get(other.id);
-        getHandle().g.remove(Integer.valueOf(other.id)); // Should be called destroyQueue
         if (entry != null && !entry.trackedPlayers.contains(getHandle())) {
             entry.updatePlayer(getHandle());
         }