[BUG] GPU config disappears permanently when GPU is hot-unplugged

[lapsio]

Describe the bug

Adding gpuX to displayed boxes will make it downgrade to stock shown_boxes = "cpu mem net proc" if said GPU is not currently registered by driver (eg. it's temporarily bound to VFIO driver to pass-through to VM)

To Reproduce

1. Add gpu0 gpu1 to system with 2 GPUs.
2. Unbind second GPU from driver / remove second GPU from system.
3. Observe that all GPUs are missing from displayed boxes

Expected behavior

Btop should preserve configuration and skip temporarily missing GPUs runtime-level, without hard-adjusting config to temporary environmental change.

Info (please complete the following information):

• btop++ version: btop version: 1.3.2
• Binary: from repo
• Architecture: x86_64
• Platform: Linux
• (Linux) Kernel: 6.10.1-arch1-1
• Terminal used: Konsole
• Font used: dunno