Fix to invisible defibrillators

Not only was the icon_state nomenclature broken to start with when the
defibrilator wound up empty, but we lacked a sprite for empty
defibrillators with paddles out. This should address that

- Add 'out of charge paddles out' defib sprite
- Fix invisible defibs
Changeloging
Merge pull request #2117 from dylanstrategie/Defibrilator

Fix to invisible defibrillators