When using a shovel it creates a hole for a cave, and your shovel goes away. It also creates a light inside the cave at the entrance. Here are the runtime errors:
runtime error: Undefined operation: null / null
proc name: Move (/lightsource/proc/Move)
source file: d4y_DFL Shading.dm,348
usr: Phriend (/mob/Player)
src: /lightsource (/lightsource)
call stack:
/lightsource (/lightsource): Move(Dirt (397,275,2) (/turf/Dirt), null, null, 0)
(/obj/Mapobj/HoleLight): New(Dirt (397,275,2) (/turf/Dirt), (/obj/Mapobj/Hole))
(/obj/Mapobj/HoleLight): New(Dirt (397,275,2) (/turf/Dirt), (/obj/Mapobj/Hole))
(/obj/Mapobj/HoleLight): New(Dirt (397,275,2) (/turf/Dirt), (/obj/Mapobj/Hole))
(/obj/Mapobj/Hole): New(Dirt (397,275,1) (/turf/Dirt))
Shovel (/obj/Items/Weapons/Shovel): MouseDrop(Dirt (397,275,1) (/turf/Dirt))
Shovel (/obj/Items/Weapons/Shovel): RightClick(Phriend (/mob/Player))
Shovel (/obj/Items/Weapons/Shovel): Click("1,9", "default.Inventory", "icon-x=55;icon-y=19;right=1;dr...")