*hard* depends on default or mcl, not optionally

[TheEt1234]

Game: devtest

ModError: Failed to load and run script from /home/et/.minetest/mods/digilines/init.lua:
/home/et/.minetest/mods/digilines/inventory.lua:172: attempt to index field 'sounds' (a nil value)
stack traceback:
	/home/et/.minetest/mods/digilines/inventory.lua:172: in main chunk
	[C]: in function 'dofile'
	/home/et/.minetest/mods/digilines/init.lua:88: in main chunk
Check debug.txt for details.

Problematic segment: https://github.com/minetest-mods/digilines/blob/master/inventory.lua#L172C11-L172C54

Solution: If no default mod then no sound