i_video: cmap_to_fb silently treats unsupported bpp as 32 instead of calling I_Error

[sunsided]

Context

cmap_to_fb in room/src/doom/i_video.rs dispatches between the 16-bpp and 32-bpp framebuffer paths based on s_Fb.bits_per_pixel.

C behavior

i_video.c calls I_Error for any bits_per_pixel other than 16 or 32, aborting the program.

Rust behavior

The Rust port falls through to the 32-bpp path for any value that is not 16. If bits_per_pixel is corrupted, the function writes garbage rather than crashing.

Location

room/src/doom/i_video.rs:196 (flagged with // FIXME:).

Suggested fix

After the bpp == 16 early return, panic / call the Rust equivalent of I_Error when bpp != 32.