fix crash in airportobject when adding to movement positions, hide none flag for airportobjectflags

Author: LeftofZen

Gui/ViewModels/LocoTypes/Objects/AirportViewModel.cs

@@ -1,6 +1,7 @@
 using Dat.Loaders;
 using Definitions.ObjectModels.Objects.Airport;
 using Definitions.ObjectModels.Objects.Common;
+using PropertyModels.ComponentModel.DataAnnotations;
 using PropertyModels.Extensions;
 using System.ComponentModel;
 using System.ComponentModel.DataAnnotations;
@@ -11,6 +12,7 @@ namespace Gui.ViewModels;
 public class AirportViewModel(AirportObject model)
 	: LocoObjectViewModel<AirportObject>(model)
 {
+	[EnumProhibitValues<AirportObjectFlags>(AirportObjectFlags.None)]
 	public AirportObjectFlags Flags
 	{
 		get => Model.Flags;

Gui/ViewModels/Pos3ViewModel.cs

@@ -5,7 +5,7 @@ namespace Gui.ViewModels;
 
 public class Pos3ViewModel : MiniReactiveObject
 {
-	public Pos3 Pos;
+	public Pos3 Pos = new();
 
 	public coord_t X
 	{