Core/Units: ported another crashfix from TC

src/server/game/Entities/Unit/Unit.cpp

@@ -13604,6 +13604,13 @@ void Unit::_ExitVehicle(Position const* exitPosition)
     // This should be done before dismiss, because there may be some aura removal
     VehicleSeatAddon const* seatAddon = m_vehicle->GetSeatAddonForSeatOfPassenger(this);
     Vehicle* vehicle = m_vehicle->RemovePassenger(this);
+
+    if (!vehicle)
+    {
+        TC_LOG_ERROR("entities.vehicle", "RemovePassenger() couldn't remove current unit from vehicle.");
+        return;
+    }
+
     Player* player = ToPlayer();
 
     // If the player is on mounted duel and exits the mount, he should immediatly lose the duel