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/BarotraumaServer.csproj

@@ -89,6 +89,7 @@
     <Compile Include="Source\PlayerInput.cs" />
     <Compile Include="Source\Program.cs" />
     <Compile Include="Source\Screens\NetLobbyScreen.cs" />
+    <Compile Include="Source\Screens\UnimplementedScreen.cs" />
     <Compile Include="Source\Sprite\Sprite.cs" />
     <Compile Include="Source\Utils\XnaToConsoleColor.cs" />
   </ItemGroup>

BarotraumaServer/Source/GameMain.cs

@@ -39,13 +39,13 @@ namespace Barotrauma
         //null screens because they are not implemented by the server,
         //but they're checked for all over the place
         //TODO: maybe clean up instead of having these constants
-        public const Screen MainMenuScreen = null;
-        public const Screen LobbyScreen = null;
+        public static readonly Screen MainMenuScreen = UnimplementedScreen.Instance;
+        public static readonly Screen LobbyScreen = UnimplementedScreen.Instance;
 
-        public const Screen ServerListScreen = null;
+        public static readonly Screen ServerListScreen = UnimplementedScreen.Instance;
 
-        public const Screen EditMapScreen = null;
-        public const Screen EditCharacterScreen = null;
+        public static readonly Screen EditMapScreen = UnimplementedScreen.Instance;
+        public static readonly Screen EditCharacterScreen = UnimplementedScreen.Instance;
 
         //
 

BarotraumaServer/Source/Screens/NetLobbyScreen.cs

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

BarotraumaServer/Source/Screens/UnimplementedScreen.cs

@@ -0,0 +1,21 @@
+using System;
+using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Graphics;
+using Barotrauma.Networking;
+using System.Linq;
+using System.Collections.Generic;
+using System.Reflection;
+using System.ComponentModel;
+
+namespace Barotrauma
+{
+    class UnimplementedScreen : Screen
+    {
+        public static readonly UnimplementedScreen Instance = new UnimplementedScreen();
+
+        public override void Select()
+        {
+            throw new Exception("Tried to select unimplemented screen");
+        }
+    }
+}

BarotraumaShared/Source/Map/Submarine.cs

@@ -175,7 +175,7 @@ namespace Barotrauma
         public bool AtEndPosition
         {
             get 
-            { 
+            {
                 if (Level.Loaded == null) return false;
                 return (Vector2.Distance(Position + HiddenSubPosition, Level.Loaded.EndPosition) < Level.ExitDistance);
             }