If you’re certain the hog box is empty, then I would clean it out – not least to get rid of any potential parasites and their eggs. It’s best to use boiling water which should kill any parasite eggs hidden in the cracks and joints.
You will need to dispose of the old ‘bedding’ and it’s best to just put a handful of fresh bedding in the box and leave more in the surrounding area.
More information: https://www.hedgehogstreet.org/cleaning-out-boxes/
Good luck – hope you get a new tenant in the newly cleaned hog house.