Core/GameObject: Cast Pickup spell of GAMEOBJECT_TYPE_FLAGSTAND

Port From (https://github.com/TrinityCore/TrinityCore/commit/bef005e34617462fc166260f5002cf79b161db59)

Source/Game/Entities/GameObject/GameObject.cs

@@ -2293,9 +2293,16 @@ namespace Game.Entities
                         if (player.GetVehicle() != null)
                             return;
 
+                        if (HasFlag(GameObjectFlags.InUse))
+                            return;
+
+                        if (!MeetsInteractCondition(player))
+                            return;
+
                         player.RemoveAurasByType(AuraType.ModStealth);
                         player.RemoveAurasByType(AuraType.ModInvisibility);
-                        return;                                     //we don;t need to delete flag ... it is despawned!
+                        spellId = GetGoInfo().FlagStand.pickupSpell;
+                        spellCaster = null;
                     }
                     break;
                 }