Deleting a product never removes bills
Deleting a product that was ever sold or bought now switches it off instead, so bills and stock history stay complete. Only unused products are deleted.
What was wrong
Deleting products, one at a time with force or in bulk, could also remove bill lines that contained them, and a bill left with no lines.
What changed
A product that was ever sold or bought is now switched off instead of deleted, whatever option is chosen. Only products with no sales or purchases are actually deleted. The old tool that removed bills with no lines was taken out.