SNIP-12 Incorrect encoding for empty enum variant

[sgc-code]

Describe the bug
Regarding SNIP-12.
Incorrect encoding for enum with no args

let consider an enum like this:

"Fee Mode": [
    { name: "No Fee", type: "()" },
    { name: "Pay Fee", type: "(uint128)" },
],

when trying to encode the first variant:
{ "No Fee": [] }

sn.js will calculate it like:
hashMethod([variantIndex, 0])

but it should be
hashMethod([typeHash, variantIndex])

there are two bugs in this example:

• first it's missing the typehash but that was already fixed in fix: correct enum typed data hashing #1281
• the seconded issue is the extra 0 at the end. this is the bug i want to report here and i happens only when the enum variant has no arguments

To Reproduce
Steps to reproduce the behavior:

Try to encode a type with an enum like this one

"Fee Mode": [
    { name: "No Fee", type: "()" },
    { name: "Pay Fee", type: "(uint128)" },
],

Expected behavior
Encoding should follow the spec and add no extra 0

Screenshots

Desktop (please complete the following information):

• Node version: 18
• Starknet.js version: v6.23.1 (latest)

Additional context