Core/Vehicle: Fix an assertion when applying SPELL_AURA_SET_VEHICLE_ID on creatures that are already vehicles

Port From (https://github.com/TrinityCore/TrinityCore/commit/53f0f2e5da3e7e6a9e6fa926e2f51ac8b506caa9)

Source/Game/Entities/Vehicle.cs

@@ -42,7 +42,7 @@ namespace Game.Entities
             // Set or remove correct flags based on available seats. Will overwrite db data (if wrong).
             if (UsableSeatNum != 0)
                 _me.SetNpcFlag(_me.IsTypeId(TypeId.Player) ? NPCFlags.PlayerVehicle : NPCFlags.SpellClick);
-            else
+            else if(unit.m_unitData.InteractSpellID == 0)
                 _me.RemoveNpcFlag(_me.IsTypeId(TypeId.Player) ? NPCFlags.PlayerVehicle : NPCFlags.SpellClick);
 
             InitMovementInfoForBase();

Source/Game/Spells/Auras/AuraEffect.cs

@@ -4961,13 +4961,23 @@ namespace Game.Spells
 
             int vehicleId = GetMiscValue();
 
+            target.RemoveVehicleKit();
+
             if (apply)
             {
                 if (!target.CreateVehicleKit((uint)vehicleId, 0))
                     return;
             }
-            else if (target.GetVehicleKit() != null)
-                target.RemoveVehicleKit();
+            else
+            {
+                Creature creature = target.ToCreature();
+                if (creature != null)
+                {
+                    uint originalVehicleId = creature.GetCreatureTemplate().VehicleId;
+                    if (originalVehicleId != 0)
+                        creature.CreateVehicleKit(originalVehicleId, creature.GetEntry());
+                }
+            }
 
             if (!target.IsTypeId(TypeId.Player))
                 return;