fix: Fixes guards attacking mobs (#2145)

### Summary

- Fixes infinite teleport from guard refactor for spawners
- Fixes guards not attacking Always Murderer creatures
- Fixes crash when calling guards due to map modification while enumeration

Projects/UOContent/Mobiles/Guards/BaseGuard.cs

@@ -203,6 +203,8 @@ public class GuardIdleTimer : Timer
             {
                 BaseGuard.TeleportTo(_owner, _owner.Spawner.HomeLocation);
             }
+
+            Stop();
         }
     }
 }