fix: fix opchecksig bug

[bloomingpeach]

• [x] fixes #211
• [x] fixes #212
• [x] follows contribution guide
• [ ] code change includes tests

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[b-j-roberts]

Hey, were you able to track down which line was giving the index out-of-bounds error? I'm curious where it was failing

[bloomingpeach]

it fails here: https://github.com/keep-starknet-strange/shinigami/blob/main/packages/engine/src/signature/signature.cairo#L298

By the way I think it is not supposed to go that far with an empty pubkey, https://github.com/keep-starknet-strange/shinigami/blob/main/packages/engine/src/signature/signature.cairo#L252 I think we should at least have a check for empty pubkey before or inside this function.

[b-j-roberts]

I see, thanks for the info! I think how you did it is a good solution.

However, I think we should also add a check here for if the pk_bytes.len != 65 and return an error, since uncompressed pub keys should always be of length 65 I think.

Would need to make parse_pub_key return an error too.

[bloomingpeach]

Would you like me to include the check in this PR or should it be in another PR? @b-j-roberts

[b-j-roberts]

Would you like me to include the check in this PR or should it be in another PR? @b-j-roberts

In this PR if you can, thanks

[bloomingpeach]

@b-j-roberts please review sir