[SAS/Atmo] Space-tile heat.

[Sarah_U.]

Bug Description:
After the SM blew up, residual heat can substain in space.
The heat will pertain and the tiles won't update ever, making the area extremely hazardeous for both marine and xenos.


Steps to reproduce:
1. Overheat the area surrounding the SM.
2. Blow up the SM (Not on the regular server, please!)
3. Seek out heated tiles in the area.
4. Test out the heat dispersion and take note that some tile will not let themselves be cooled; Even in space.