So, here's a patch that forces positive health during combat. The potential issue here is that if the health would display negative through monster healing or something similar, it won't be displayed... just keep showing 1 health. Do we want to do it this way, or try to catch the adjusted (base) health modifier instead?
The other way is probably better, but would take someone else posting... my version of MonsterDatabase has been heavily tweaked at this point due to it having scaling monsters.
Edit: Another issue with this version is that it means that checking monster health outside combat can still return negative numbers. Which it obviously won't be.