Make the doors of the arrivals shuttle unweldable

[kyle2143]

It's against the rules to seal arrivals or the arrivals shuttle. It might happen on occasion that someone new does this without knowing it's illicit or just people trying to greif, but they are usually dealt with, I don't think there's a need to prevent it in code. Because then people can still wall it, or move objects, and the list goes on. More trouble than it's worth, just ahelp if someone does it.