Runtime fix and two tweaks to captain items.

Fixes a runtime caused by an away mission trying to pull atmospherics data before there is any. Thank you Skymarshal for help.

Captains will no longer spawn with armour.

Captain's PDA will spawn with messenger ON but their improved model is undetonateable.

Apologies to Asanadas and spamcat for repeating a pull request you both have done.