Adjust cross-thread error message (#4181)

Source/ACE.Server/Entity/Landblock.cs

@@ -823,6 +823,19 @@ private bool AddWorldObjectInternal(WorldObject wo)
             {
                 if (CurrentLandblockGroup != null && CurrentLandblockGroup != LandblockManager.CurrentMultiThreadedTickingLandblockGroup.Value)
                 {
+                    // Prevent possible multi-threaded crash
+                    // The following scenario can happen rarely in ACE, all in the same call stack with no ActionQueue usage:
+                    // Moster successfully lands an attack on a player that procs a cloak spell
+                    // The code goes through and does the LaunchSpellProjectiles() which adds the spell projectiles to (presumably) the players landblock
+                    // For some unknown reason, the LandblockGroup/Thread where the monster exists seems to be a different LandblockGroup/Thread where the spells are added to.
+                    // Maybe there's a player death race condition? Maybe it's a teleport race condition? I dunno.
+                    // Because this happens so rarely, and, it only seems to affect cloak projectiles, and, cloak projectiles are pretty benign, we simply don't add the object, and only log it as a warning.
+                    if (wo.WeenieType == WeenieType.ProjectileSpell)
+                    {
+                        log.Warn($"Landblock 0x{Id} entered AddWorldObjectInternal in a cross-thread operation for a ProjectileSpell. This is normally not an issue unless it's happening more than once an hour.");
+                        return false;
+                    }
+
                     log.Error($"Landblock 0x{Id} entered AddWorldObjectInternal in a cross-thread operation.");
                     log.Error($"Landblock 0x{Id} CurrentLandblockGroup: {CurrentLandblockGroup}");
                     log.Error($"LandblockManager.CurrentMultiThreadedTickingLandblockGroup.Value: {LandblockManager.CurrentMultiThreadedTickingLandblockGroup.Value}");
@@ -842,10 +855,6 @@ private bool AddWorldObjectInternal(WorldObject wo)
 
                     log.Error("PLEASE REPORT THIS TO THE ACE DEV TEAM !!!");
 
-                    // Prevent possible multi-threaded crash
-                    if (wo.WeenieType == WeenieType.ProjectileSpell)
-                        return false;
-
                     // This may still crash...
                 }
             }