Why isn't this script working?

[flamez3]

RemoveItem(asItem); it needs quotation marks around asItem.
And you missed the other quotation mark around AreaFillBucket

void OnStart()
{

// Debug
if(ScriptDebugOn())
{
GiveItemFromFile("lantern", "lantern.ent");
}

PlayMusic("02_amb_strange.ogg", true, 0.2f, 2, 0, true);
AddUseItemCallback("", "bucket_empty_1", "AreaFillBucket", "FillBucketFunc", true);
}

void FillBucketFunc(string &in asItem, string &in asEntity)
{
PlaySoundAtEntity("", "04_water_puff.snt", "AreaFillBucket", 0.0f, true);
RemoveItem("asItem");
GiveItemFromFile("filled_bucket", "wooden_bucket_filled.ent");
}

There is the script that you should use