default:unknown

This code in pchest.lua refers to a non-existent node, and anyway doesn't do anything. Anyone forking or fixing this repo should remove it.

```
            local p = pointed_thing.under
            local ab = pointed_thing.above
            local s = ItemStack("default:unknown")
            local sinv = minetest.get_meta(pointed_thing.under):get_inventory()

```