Code Quality: Prevent drag and drop race condition (#17625)

Co-authored-by: seer-by-sentry[bot] <157164994+seer-by-sentry[bot]@users.noreply.github.com>

Author: seer-by-sentry[bot]

src/Files.App/ViewModels/Layouts/BaseLayoutViewModel.cs

@@ -101,6 +101,14 @@ public async Task DragOverAsync(DragEventArgs e)
 				return;
 			}
 
+			// Check if ShellViewModel is initialized to prevent race condition
+			if (_associatedInstance.ShellViewModel is null)
+			{
+				e.AcceptedOperation = DataPackageOperation.None;
+				deferral.Complete();
+				return;
+			}
+
 			if (FilesystemHelpers.HasDraggedStorageItems(e.DataView))
 			{
 				e.Handled = true;
@@ -207,6 +215,13 @@ public async Task DropAsync(DragEventArgs e)
 				}
 			}
 
+			// Check if ShellViewModel is initialized to prevent race condition
+			if (_associatedInstance.ShellViewModel is null)
+			{
+				e.AcceptedOperation = DataPackageOperation.None;
+				return;
+			}
+
 			var deferral = e.GetDeferral();
 			try
 			{