fix crash when attempting to show vanilla object from the object service

Author: LeftofZen

Gui/Models/ObjectEditorModel.cs

@@ -212,11 +212,15 @@ bool TryLoadOnlineFile(FileSystemItemBase filesystemItem, out UiDatLocoFile? loc
 				}
 				else if (string.IsNullOrEmpty(cachedLocoObjDto.DatBytes))
 				{
-					Logger.Warning($"Unable to download object {filesystemItem.DisplayName} with unique id {uniqueObjectId} from online - received no DAT object data. Will still show metadata");
+					if (cachedLocoObjDto.ObjectSource == ObjectSource.LocomotionSteam || cachedLocoObjDto.ObjectSource == ObjectSource.LocomotionGoG)
+					{
+						Logger.Warning($"This is a vanilla object. The DAT file cannot be downloaded due to copyright. Any available metadata will still be shown.");
+					}
+					Logger.Warning($"Unable to download object {filesystemItem.DisplayName} with unique id {uniqueObjectId} from online - received no DAT object data. Any available metadata will still be shown.");
 				}
 				else if (cachedLocoObjDto.ObjectSource is ObjectSource.LocomotionSteam or ObjectSource.LocomotionGoG)
 				{
-					Logger.Warning($"Unable to download object {filesystemItem.DisplayName} with unique id {uniqueObjectId} from online - requested object is a vanilla object and it is illegal to distribute copyright material. Will still show metadata");
+					Logger.Warning($"Unable to download object {filesystemItem.DisplayName} with unique id {uniqueObjectId} from online - requested object is a vanilla object and it is illegal to distribute copyright material. Any available metadata will still be shown.");
 				}
 
 				Logger.Info($"Downloaded object {filesystemItem.DisplayName} with unique id {uniqueObjectId} and added it to the local cache");

Gui/ViewModels/DatTypes/DatObjectEditorViewModel.cs

@@ -182,11 +182,15 @@ public override void Load()
 			else
 			{
 				// todo: show warnings here
+				// in online mode, vanilla objects won't be downloaded so they hit this case, which is a valid use-case
 				CurrentObject = null;
 				CurrentObjectViewModel = null;
 			}
 		}
 
+		public string ExtraContentViewModelTabName
+			=> ExtraContentViewModel == null ? "<no content>" : ExtraContentViewModel.Name;
+
 		public override void Delete()
 		{
 			if (CurrentFile.FileLocation != FileLocation.Local)

Gui/Views/DatObjectEditorView.axaml

@@ -60,11 +60,13 @@
 						</ItemsRepeater>
 					</DockPanel>
 				</TabItem>
-				<TabItem Header="{Binding ExtraContentViewModel.Name}">
+
+				<TabItem Header="{Binding ExtraContentViewModelTabName}">
 					<DockPanel>
 						<ContentControl Content="{Binding ExtraContentViewModel}" />
 					</DockPanel>
 				</TabItem>
+
 				<TabItem Header="Metadata">
 					<Border Background="{DynamicResource ExpanderContentBackground}" Margin="8">
 						<DockPanel Margin="8">