Fixed crash when an earth pony tries to kick a tree during a world tick

src/main/java/com/minelittlepony/unicopia/Unicopia.java

@@ -59,6 +59,7 @@ import com.minelittlepony.unicopia.player.PlayerSpeciesList;
 import com.minelittlepony.unicopia.power.PowersRegistry;
 import com.minelittlepony.unicopia.spell.SpellRegistry;
 import com.minelittlepony.unicopia.util.crafting.CraftingManager;
+import com.minelittlepony.unicopia.world.UWorld;
 
 @Mod(
     modid = Unicopia.MODID,
@@ -205,6 +206,13 @@ public class Unicopia implements IGuiHandler {
         }
     }
 
+    @SubscribeEvent
+    public static void onWorldTick(TickEvent.WorldTickEvent event) {
+        if (event.phase == Phase.START) {
+            UWorld.tick(event.world);
+        }
+    }
+
     @SubscribeEvent
     public static void onPlayerTick(TickEvent.PlayerTickEvent event) {
         if (event.phase == Phase.END) {

src/main/java/com/minelittlepony/unicopia/power/PowerStomp.java

@@ -14,6 +14,7 @@ import com.minelittlepony.unicopia.particle.Particles;
 import com.minelittlepony.unicopia.player.IPlayer;
 import com.minelittlepony.unicopia.player.PlayerSpeciesList;
 import com.minelittlepony.unicopia.power.data.Location;
+import com.minelittlepony.unicopia.world.UWorld;
 import com.minelittlepony.util.MagicalDamageSource;
 import com.minelittlepony.util.PosHelper;
 import com.minelittlepony.util.WorldEvent;
@@ -168,13 +169,19 @@ public class PowerStomp implements IPower<PowerStomp.Data> {
             IPower.takeFromPlayer(player, rad);
         } else if (data.hitType == 1) {
 
-            if (player.world.rand.nextInt(30) == 0) {
+            if (player.world.rand.nextInt(5) == 0) {
-                removeTree(player.world, data.pos());
+                int cost = dropApples(player.world, data.pos());
-            } else {
-                dropApples(player.world, data.pos());
-            }
 
-            IPower.takeFromPlayer(player, 1);
+                if (cost > 0) {
+                    IPower.takeFromPlayer(player, cost / 3);
+                }
+            } else {
+                UWorld.enqueueTask(() -> {
+                    removeTree(player.world, data.pos());
+                });
+
+                IPower.takeFromPlayer(player, 3);
+            }
         }
     }
 
@@ -233,7 +240,8 @@ public class PowerStomp implements IPower<PowerStomp.Data> {
         int size = measureTree(w, log, pos);
         if (size > 0) {
             pos = ascendTrunk(new ArrayList<BlockPos>(), w, pos, log, 0);
-            removeTreePart(w, log, pos, 0);
+
+            removeTreePart( w, log, pos, 0);
         }
     }
 
@@ -303,7 +311,7 @@ public class PowerStomp implements IPower<PowerStomp.Data> {
         return pos;
     }
 
-    private void dropApples(World w, BlockPos pos) {
+    private int dropApples(World w, BlockPos pos) {
         IBlockState log = w.getBlockState(pos);
         int size = measureTree(w, log, pos);
         if (size > 0) {
@@ -312,8 +320,17 @@ public class PowerStomp implements IPower<PowerStomp.Data> {
 
             dropApplesPart(capturedDrops, new ArrayList<BlockPos>(), w, log, pos, 0);
 
-            capturedDrops.forEach(w::spawnEntity);
+            UWorld.enqueueTask(() -> {
+                capturedDrops.forEach(item -> {
+                    item.setNoPickupDelay();
+                    w.spawnEntity(item);
+                });
+            });
+
+            return capturedDrops.size() / 3;
         }
+
+        return 0;
     }
 
     private void dropApplesPart(List<EntityItem> drops, List<BlockPos> done, World w, IBlockState log, BlockPos pos, int level) {

src/main/java/com/minelittlepony/unicopia/world/UWorld.java

@@ -0,0 +1,31 @@
+package com.minelittlepony.unicopia.world;
+
+import java.util.Queue;
+
+import com.google.common.collect.Queues;
+import com.minelittlepony.jumpingcastle.Exceptions;
+import com.minelittlepony.unicopia.Unicopia;
+
+import net.minecraft.world.World;
+
+public class UWorld {
+
+    private static final Queue<Runnable> tickTasks = Queues.newArrayDeque();
+
+    private static final Object locker = new Object();
+
+    public static void tick(World world) {
+        synchronized (locker) {
+            Runnable task;
+            while ((task = tickTasks.poll()) != null) {
+                Exceptions.logged(task, Unicopia.log);
+            }
+        }
+    }
+
+    public static void enqueueTask(Runnable task) {
+        synchronized (locker) {
+            tickTasks.add(task);
+        }
+    }
+}