Gwenview does not display a custom folder icon which is configured
by an absolute path and the folder does not contain any images.
This is caused by `KIconLoader::loadMimeTypeIcon()` failing for
absolute path entries. If the folder contains images the preview
job corrects the icon later.
Using `KIconLoader::loadIcon()` loads the correct icon.
BUG: 315983
FIXED-IN: 18.04.1