fix: hexFrom in @ckb-ccc/core/barrel not producing valid hex strings when an empty array is provided

[Officeyutong]

console.log(hexFrom([])); // outputs "0x"
console.log(hexFrom(new Uint8Array([]))); // outputs "0x"

hexFrom will return 0x which is an invalid hex string when an empty array was provided as argument, since bytesTo returns empty string when zero-length bytes was provided.

Illegal hex string like 0x will be refused by BigInt and leads to an exception.

This PR fixes it by providing a default "0" if bytesTo returns an empty string.

[changeset-bot]

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[Hanssen0]

This is the intended behaviour. hexFrom is not designed for numeric values but raw bytes data.

For example, if a cell's data is "0x", it stores empty data. But if it's "0x0", it has one byte.

ccc.numFrom and ccc.numFromBytes are designed for transforming bytes/hex number to bigint.

[Officeyutong]

This is the intended behaviour. hexFrom is not designed for numeric values but raw bytes data.

For example, if a cell's data is "0x", it stores empty data. But if it's "0x0", it has one byte.

ccc.numFrom and ccc.numFromBytes are designed for transforming bytes/hex number to bigint.

Thank you!

But this issue comes from another issue:
If epochFromHex was called with string 0x0 (Seems the genesis block has this epoch), it may call numFrom with an empty array, and numFrom will call BigInt(hexFrom(val)) and lead to an exception

[Hanssen0]

Please check if #92 fix epochFromHex

[Officeyutong]

Please check if #92 fix epochFromHex

It's fixed now, thank you!