From 5c7fd8666a8592b0a0c19a5857d2747c0086ebfc Mon Sep 17 00:00:00 2001
From: Alex Warren <alex@alexwarren.uk>
Date: Tue, 14 Apr 2026 14:27:15 +0100
Subject: [PATCH] Fix unhandled exceptions in WorldModel crashing the server

GetObjectsInScope could return null when RunScript catches a script
error and returns null - the foreach in GetExitsListData (and
UpdateObjectsList) would then throw NullReferenceException. Return an
empty list instead.

UpdateLists() was called outside the try-catch in SendCommand, Tick,
and RunCallbackAndFinishTurn. Since these all run on threads spawned
by DoInNewThreadAndWait, an unhandled exception there crashes the
whole process. Moved UpdateLists() inside the existing try-catch in
each case.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 src/Engine/WorldModel.cs | 30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/src/Engine/WorldModel.cs b/src/Engine/WorldModel.cs
index acd251381..81ca4462b 100644
--- a/src/Engine/WorldModel.cs
+++ b/src/Engine/WorldModel.cs
@@ -244,7 +244,7 @@ private QuestList<Element> GetObjectsInScope(string scopeFunction)
     {
         if (Elements.ContainsKey(ElementType.Function, scopeFunction))
         {
-            return (QuestList<Element>)RunProcedure(scopeFunction, true)!;
+            return (QuestList<Element>?)RunProcedure(scopeFunction, true) ?? new QuestList<Element>();
         }
         throw new Exception($"No function '{scopeFunction}'");
     }
@@ -530,17 +530,16 @@ public void SendCommand(string command, int elapsedTime, IDictionary<string, str
                     {
                         TryFinishTurn();
                     }
+                    if (State != GameState.Finished)
+                    {
+                        UpdateLists();
+                    }
                 }
                 catch (Exception ex)
                 {
                     LogException(ex);
                 }
 
-                if (State != GameState.Finished)
-                {
-                    UpdateLists();
-                }
-
                 ChangeThreadState(ThreadState.Ready);
             }
             else
@@ -1337,14 +1336,14 @@ public void Tick(int elapsedTime)
                 {
                     RunScript(timerScript.Value, timerScript.Key);
                 }
+
+                UpdateLists();
             }
             catch (Exception ex)
             {
                 LogException(ex);
             }
 
-            UpdateLists();
-
             ChangeThreadState(ThreadState.Ready, false);
         });
 
@@ -1414,11 +1413,18 @@ public void SetQuestionResponse(bool response)
 
     private void RunCallbackAndFinishTurn(Callback callback)
     {
-        RunScript(callback.Script, callback.Context);
-        TryFinishTurn();
-        if (State != GameState.Finished)
+        try
         {
-            UpdateLists();
+            RunScript(callback.Script, callback.Context);
+            TryFinishTurn();
+            if (State != GameState.Finished)
+            {
+                UpdateLists();
+            }
+        }
+        catch (Exception ex)
+        {
+            LogException(ex);
         }
         ChangeThreadState(ThreadState.Ready);
         SendNextTimerRequest();