* 4.6.7-1
 * Arch Linux
 * AMD Raven Ridge (amdgpu)
 * 64 bit
 * (no relevant errors in log)

Issue
"Backgrounds" settings app does not accept legal filename. Specifically, a filename with %20 in it.

Steps to reproduce

1. Download https://raw.githubusercontent.com/elementary/wallpapers/c5a5e8208a851069bf93b3ccdab7bac158efa11f/Pablo%20Garcia%20Saldana.jpg
2. Name the file Pablo%20Garcia%20Saldana.jpg with the %20
3. Move to a directory that the "Background" app sources for images
4. Select the image thumbnail
5. The background will not change to that image; (for me, it changes to Adwaita 7680x4320)
6. Replace the %20 in the filenames with
7. Re-open the background app
8. Select the thumbnail
9. The background will be set correctly

Expected behaviour
Any filename works correctly