My desktop was configured to use a monochromatic dark grey background. I wanted some color back, so I configured my desktop to use one of the wallpapers that come with plasma. After applying my choice, the images in the image selection widget disappeared, and only three black bars at the top remained.

Steps to reproduce:
1. Apply monochrome backround
2. Close the configure dialog completely
3. Open it again
4. Change "monochrome" to "image" (my translation from the German version)
5. Select any image
6. Apply

Actual result:
The image selection widget is cleared. If I chose an image from the top row, three black bars appear at the top of the image.

Expected result:
No change at all when I click Apply.

Reproducible: every time