wallpapers/image: don't add/remove a file if its parent folder is in KDirWatch
Otherwise KDirWatchPrivate::removeEntry will also remove the parent folder when the file is removed from KDirWatch. See https://invent.kde.org/frameworks/kcoreaddons/-/blob/396c75c24ad223bce50302569d42dc4b55bb4580/src/lib/io/kdirwatch.cpp?page=2#L1103 Amends bdbe9b33