after_place_node = function(pos, placer)
		whoplacedit = placer:get_player_name()
		print(whoplacedit)
		node = minetest.env:get_node(pos)
		ntop = minetest.env:get_node({x=pos.x, y=pos.y+1, z=pos.z})
		if ntop.name ~= "air" then
			minetest.node_dig(pos, node, whoplacedit)
		end
	end,

output on terminal:

singleplayer
node_dig
02:17:16: ACTION[ServerThread]: singleplayer leaves game. List of players:
02:17:17: ERROR[main]: ServerError: LuaError: error: ...a/celeron55-minetest-9696ed3/bin/../builtin/item.lua:286: attempt to call method 'get_player_name' (a nil value)
02:17:17: ERROR[main]: stack traceback:
Quit message received.
vanessa@rainbird:~$