BlockChunkWorld

Hi, I am trying to add an block drop event so that ice will drop a random amount of ice shards on breaking, and it works fine. However, if I try breaking the ice with only my hand, I get a crash. What am I doing wrong? if (event.block == Blocks.ice && event.harvester.getHeldItem().getItem() != BlocksMod.IceSaw) event.drops.add(new ItemStack(BlocksMod.IceShard, r.nextInt(4) + 0)); Thanks in advance!