Core/Vehicles: Implemented vehicle seat flag that makes passengers unselectable and dropped redundant UNIT_STATE_ONVEHICLE (it is only checked in the same places as unselectable unit flag)

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

@@ -16855,7 +16855,7 @@ void Unit::ChangeSeat(int8 seatId, bool next)
 
     SeatMap::const_iterator seat = (seatId < 0 ? m_vehicle->GetNextEmptySeat(GetTransSeat(), next) : m_vehicle->Seats.find(seatId));
     // The second part of the check will only return true if seatId >= 0. @Vehicle::GetNextEmptySeat makes sure of that.
-    if (seat == m_vehicle->Seats.end() || seat->second.Passenger)
+    if (seat == m_vehicle->Seats.end() || !seat->second.IsEmpty())
         return;
 
     AuraEffect* rideVehicleEffect = NULL;
@@ -17261,7 +17261,7 @@ void Unit::OutDebugInfo() const
     {
         o << "Passenger List: ";
         for (SeatMap::iterator itr = GetVehicleKit()->Seats.begin(); itr != GetVehicleKit()->Seats.end(); ++itr)
-            if (Unit* passenger = ObjectAccessor::GetUnit(*GetVehicleBase(), itr->second.Passenger))
+            if (Unit* passenger = ObjectAccessor::GetUnit(*GetVehicleBase(), itr->second.Passenger.Guid))
                 o << passenger->GetGUID() << ", ";
         TC_LOG_INFO(LOG_FILTER_UNITS, "%s", o.str().c_str());
     }