Fixed any chance of creatures .getTarget throwing a class cast exception - thanks to an old PR by garbagemule!

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

@@ -24,6 +24,7 @@ public class CraftCreature extends CraftLivingEntity implements Creature {
 
     public CraftLivingEntity getTarget() {
         if (getHandle().target == null) return null;
+        if (!(getHandle().target instanceof CraftLivingEntity)) return null;
 
         return (CraftLivingEntity) getHandle().target.getBukkitEntity();
     }