Fix Campifires API to not crash the server.

Fixed the error in Campfires' On_RightClick() to not error out when called with a non-existent pointed_thing.

mods/ITEMS/mcl_campfires/api.lua

@@ -332,6 +332,9 @@ function mcl_campfires.register_campfire(name, def)
 			elseif minetest.get_item_group(itemstack:get_name(), "campfire_cookable") ~= 0 then
 				mcl_campfires.take_item(pos, node, player, itemstack)
 			else
+				if not pointed_thing then
+					return itemstack
+				end
 				minetest.item_place_node(itemstack, player, pointed_thing)
 			end
 		end,