Panic on "Keypad Test" ROM

[orsinium]

The ROM:

https://github.com/kripod/chip8-roms/blob/master/programs/Keypad%20Test%20%5BHap%2C%202006%5D.ch8

rsc8 first renders wrong picture and then panics.

thread 'main' (214688) panicked at rsc8_core/src/chip8.rs:349:35:
attempt to multiply with overflow
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:689:5
   1: core::panicking::panic_fmt
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/panicking.rs:80:14
   2: core::panicking::panic_const::panic_const_mul_overflow
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/panicking.rs:175:17
   3: rsc8_core::chip8::Chip8<R>::execute_instruction
             at ./rsc8_core/src/chip8.rs:349:35
   4: rsc8_core::chip8::Chip8<R>::tick
             at ./rsc8_core/src/chip8.rs:94:14
   5: rsc8_tui::run
             at ./rsc8_tui/src/main.rs:79:19
   6: rsc8_tui::main
             at ./rsc8_tui/src/main.rs:39:18
   7: core::ops::function::FnOnce::call_once
             at /home/gram/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.