Extra error checking.

deco_rocks.lua

@@ -1,5 +1,9 @@
 -- Place a small nodebox.
 local function small_cube(grid, pos, diameters)
+	if not (grid and pos and diameters and type(grid) == 'table' and type(diameters) == 'table') then
+		return
+	end
+
 	local rock = {}
 
 	rock[1] = pos.x
@@ -83,6 +87,10 @@ minetest.register_node("fun_caves:small_rocks", {
 	groups = {stone=1, oddly_breakable_by_hand=3, dig_immediate = 3},
 	sounds = default.node_sound_stone_defaults(),
 	after_place_node = function(pos, placer, itemstack, pointed_thing)
+		if not pos then
+			return
+		end
+
 		minetest.set_node(pos, {name = "fun_caves:small_rocks"..math.random(6)})
 	end,
 })