Cloud block shows mining progress but is indestructable

[satoshinm]

[satoshinm]

The reason why it doesn't destruct is this in src/item.c:

bool is_destructable(int w) {
    switch (w) {
        case EMPTY:
        case CLOUD:
            return false;
        default:
            return true;
    }
}

Remove is_destructable now that there is the hardness property, and it can return INFINITY?