Itch.io games lose vertical images, don't load in correctly #679

When starting GameHub up, games from Itch.io will not load correctly. Any vertical images that I might have saved the last time I opened GameHub will have disappeared, and I will have to redownload them (oddly, some of the regular/horizontal images seem to persist; however, I use a vertical layout so this is not ideal). This only happens for Itch.io games; the images for all my other games are fine.

Additionally, even though I have "group by status" turned on, my installed Itch.io games will be mixed in with the uninstalled games when I start up GameHub. If I open the Filters menu and change the "group by" setting to "do not group", and then change it back to "by status", the Itch.io games will at last be correctly sorted.

I am combining these two problems into one bug report because I wonder if there might be a common core issue; i.e. perhaps GameHub is not saving metadata correctly for Itch.io games.

Version and environment

- GameHub
    Version: 0.16.3-b28e01d-master
    Branch:  master
    Commit:  b28e01dcdc1bd2e2499c0e6f53ded953e5aa9e75
- Environment
    Distro:  Ubuntu 22.04.3 LTS
    DE:      ubuntu:GNOME
    GTK:     3.24.33
    Themes:  Yaru-magenta-dark | Yaru-magenta