0.51: Custom order lost when closing options dialog

[helmut]

When closing the options dialog, the previously generated custom sort order is lost.

To reproduce:
1. Start XnView and open a folder with several files
2. Create a custom order by dragging the files.
3. Open options dialog (F12 key)
4. Close options using 'Cancel' button
--> Sort order of files changes. Custom order is lost.