When attempting to mark as read an IMAP folder that has subfolders, the "Mark as read" plugin pops up a dialog asking "Do you want the operation to be performed also in the subfolders?", even when none of the subfolders have unread items, or when they're all empty. 

What should happen:

 * If at least one subfolder has unread items, the question is relevant, and should be asked

 * If no subfolders have unread items, but the parent folder does, the question isn't relevant, and only the parent folder should be marked as read without asking anything


Other information: