Fixed entities targetting other entities outside the border

src/main/java/com/songoda/skyblock/listeners/Entity.java

@@ -248,6 +248,37 @@ public class Entity implements Listener {
 		}
 	}
 
+	/**
+	 * Checks that an entity is not targeting another entity on different islands.
+	 * @author LimeGlass
+	 */
+	@EventHandler
+	public void onEntityTarget(EntityTargetEvent event) {
+		org.bukkit.entity.Entity entity = event.getEntity();
+		WorldManager worldManager = skyblock.getWorldManager();
+		if (!worldManager.isIslandWorld(entity.getWorld()))
+			return;
+
+		org.bukkit.entity.Entity target = event.getTarget();
+
+		IslandManager islandManager = skyblock.getIslandManager();
+		Island entityIsland = islandManager.getIslandAtLocation(entity.getLocation());
+		Island targetIsland = islandManager.getIslandAtLocation(target.getLocation());
+		// Event not related to Skyblock islands.
+		if (entityIsland == null && targetIsland == null)
+			return;
+		// One entity is on an island, and the other isn't.
+		if (entityIsland == null || targetIsland == null) {
+			event.setCancelled(true);
+			return;
+		}
+		// Both entities are on different islands.
+		if (!entityIsland.getIslandUUID().equals(targetIsland.getIslandUUID())) {
+			event.setCancelled(true);
+			return;
+		}
+	}
+
 	@EventHandler
 	public void onStackableInteract(PlayerArmorStandManipulateEvent event) {
 		Player player = event.getPlayer();