set_current_mode seems to panic on at least QEmu

[tomaka]

redshirt/modules/vga-vbe/src/main.rs

Line 152 in fce170a

vbe.set_current_mode(chosen_mode_num).await.unwrap();

I'm not actually sure that there's a panic, but everything seems to point to this direction.
It's unfortunately hard to figure out, because the video mode is half-way done when the panic allegedly happens.

Needs #682