Ace Dev FIx

I have added null safety checks to the medical damage manager and cardiac arrest exit logic so that the server no longer crashes when characters spawn before their hit zones
  register, or when cleanup runs after a character has already been destroyed. AI characters now skip the ACE medical math entirely, since they don't benefit from it and were
  contributing most of the crash spam during firefights.

  Credits
  Original Mod: ACE Medical Dev
  This is a personal fix/patch. All credits for the original code belong to the ACE team.