Avoid Bukkit error with water potions.

src/com/massivecraft/mcore/util/MUtil.java

@@ -316,6 +316,17 @@ public class MUtil
 		return item.getDurability() & 0x3F;
 	}
 	
+	/**
+	 * Checks if the given potion is a vial of water.
+	 *
+	 * @param item the item to check
+	 * @return true if it's a water vial
+	 */
+	public static boolean isWaterPotion(ItemStack item)
+	{
+		return getPotionEffectBits(item) == 0;
+	}
+	
 	public static List<PotionEffect> getPotionEffects(ItemStack itemStack)
 	{
 		if (itemStack == null) return null;
@@ -323,6 +334,8 @@ public class MUtil
 
 		List<PotionEffect> ret = new ArrayList<PotionEffect>();
 		
+		if (isWaterPotion(itemStack)) return ret;
+		
 		Potion potion = Potion.fromDamage(getPotionEffectBits(itemStack));
 		ret.addAll(potion.getEffects());