fix: handle null maps when deactivating creature AI (#2629)

An uncontrolled creature with `Map == null` throws in `BaseAI.Deactivate()` when the condition reaches `Map.GetSector()`. A controlled creature with a null map avoids the exception but leaves its AI timer running.

Treat a null map like `Map.Internal` in the existing stop condition. This stops the timer without dereferencing the missing map and leaves the existing valid-map condition and return-home scheduling unchanged.

Addresses only the null-map `Deactivate()` item in #2627; the other audit items remain separate. No era-specific rules are changed.

Projects/UOContent.Tests/Tests/Mobiles/AI/AIDeactivationTests.cs

@@ -0,0 +1,33 @@
+using Server;
+using Xunit;
+
+namespace UOContent.Tests.Mobiles.AI;
+
+[Collection("Sequential UOContent Tests")]
+public class AIDeactivationTests
+{
+    [Theory]
+    [InlineData(false, false)]
+    [InlineData(false, true)]
+    [InlineData(true, false)]
+    [InlineData(true, true)]
+    public void Deactivate_WithoutWorldMap_StopsTimer(bool internalMap, bool controlled)
+    {
+        var creature = new PetTestStub();
+        try
+        {
+            creature.Controlled = controlled;
+            creature.Map = internalMap ? Map.Internal : null;
+            creature.AIObject.Activate();
+            Assert.True(creature.AIObject.AITimer.Running);
+
+            creature.AIObject.Deactivate();
+
+            Assert.False(creature.AIObject.AITimer.Running);
+        }
+        finally
+        {
+            creature.Delete();
+        }
+    }
+}

Projects/UOContent/Mobiles/AI/BaseAI/BaseAI.cs

@@ -1102,7 +1102,7 @@ public abstract partial class BaseAI
 
     public virtual void Deactivate()
     {
-        if (Mobile.Map == Map.Internal || !Mobile.Controlled && !Mobile.Map.GetSector(Mobile.Location).Active)
+        if (Mobile.Map == null || Mobile.Map == Map.Internal || !Mobile.Controlled && !Mobile.Map.GetSector(Mobile.Location).Active)
         {
             AITimer.Stop();
         }