Fixes commstones breaking sometimes
Created by: Exxion
For some reason, BYOND treats variables that have lists assigned to them exclusively as references to the lists. So making one list, setting another variable equal to it, and editing that new variable actually edits the first list. This is not mentioned anywhere in the DM reference for some inconceivable reason.
So if someone attempted to use a commstone while the base station was unpowered, the check for active stones would remove any stones that had ever been removed from the base station from the base station's list of associated stones.
Fixes #9562 (closed)