[Bug] Greeter fails to load user settings if the wallpaper file is too big

[TerMyY]

Issue:
If user has a desktop wallpaper of a certain size (I had issues with 19MB and 15MB pngs), cosmic-greeter will not load the image, as well as any other user settings such as accent color, time format preference and keyboard layouts. Some of PopOS default wallpapers are >15MB and cause this issue

Steps to reproduce:

1. In cosmic-settings, choose a custom directory
2. Select a file over 15MB in size as your wallpaper
3. log out or reboot

Expected behavior:
Cosmic-greeter correctly loads the image and the rest of user preferences.

Version: cosmic-greeter 0.1.0 (git commit epoch-1.0.5); NixOS Unstable (26.05)