Fix: Fixed NullReferenceException in folder.GetThumbnailAsync (#12286)

Author: hecksmosis

src/Files.App/Data/Items/DriveItem.cs

@@ -248,10 +248,12 @@ public async Task LoadThumbnailAsync(bool isSidebar = false)
 			{
 				if (!string.IsNullOrEmpty(DeviceID) && !string.Equals(DeviceID, "network-folder"))
 					IconData ??= await FileThumbnailHelper.LoadIconWithoutOverlayAsync(DeviceID, 24);
-
-				using var thumbnail = await DriveHelpers.GetThumbnailAsync(Root);
-				IconData ??= await thumbnail.ToByteArrayAsync();
-
+				
+				if (Root is not null)
+				{
+					using var thumbnail = await DriveHelpers.GetThumbnailAsync(Root);
+					IconData ??= await thumbnail.ToByteArrayAsync();
+				}
 				IconData ??= UIHelpers.GetSidebarIconResourceInfo(Constants.ImageRes.Folder).IconData;
 			}