Panic on invalid CPU modes

[xTibor]

thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', rustboyadvance-core/src/arm7tdmi/psr.rs:73:9

Games hitting this panic:

• Madden NFL 2002 (after the BIOS logo)
• Starsky & Hutch (after starting a new game)
• Ultimate Muscle - The Kinnikuman Legacy
• Banjo-Kazooie - Grunty's Revenge
• The Powerpuff Girls - Mojo Jojo A-Go-Go
• Colin McRae Rally 2.0
• Gauntlet - Dark Legacy

[michelhe]

*closed by mistake

I don't recall having this panic when playin madden NFL 2002.

I'll try to do a bisect and look into it in the weekend, this could be a regression

[michelhe]

I was hoping open-bus will solve these too, but nope.