Resolve get_first clippy lint
Resolve get_first clippy lint

    error: accessing first element with `slice.as_bytes().get(0)`
       --> src/error.rs:441:11
        |
    441 |     match slice.as_bytes().get(0) {
        |           ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `slice.as_bytes().first()`
        |
        = note: `-D clippy::get-first` implied by `-D clippy::all`
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#get_first

serde-rs/json