Ignore unrecognized keyboard modifiers
Ignore unrecognized keyboard modifiers

Fixes a crash when pressing any key on linux

Rust-SDL2/rust-sdl2,Rust-SDL2/rust-sdl2,Cobrand/rust-sdl2,Rust-SDL2/rust-sdl2,Cobrand/rust-sdl2,Cobrand/rust-sdl2,vadixidav/rust-sdl2,AngryLawyer/rust-sdl2