Trying to address invisible defibs again

- Fix mistake in update_icon() proc that caused the defib to stay
invisible when out of power
- Remove src. typecasting, formatting
- Try to clarify messages, notably since it leads to doctors believing
they are treating unrevivable bodies when the ghost simply didn't
re-enter body yet
Add suggestion, avoid hardcoding
Merge pull request #2178 from dylanstrategie/Defib

Trying to address invisible defibs again