Fixed linked subs not spawning

Turns out the game actually sets Screen.Selected to null when the game starts, so the server would break on EditMapScreen checks.

BarotraumaServer/Source/Screens/NetLobbyScreen.cs

@@ -50,7 +50,7 @@ namespace Barotrauma
 
         public override void Select()
         {
-            
+
         }
 
         private List<Submarine> subs;