grav1synth inspect return index out of range

[tuanden0]

@shssoichiro

from latest commit on main branch

I got error when using grav1synth inspect in.mkv -o grain.txt

thread 'main' panicked at src\parser\obu.rs:203:27:
range start index 18446744073709551615 out of range for slice of length 1185
stack backtrace:
0: 0x7ff732c3b309 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h8340f5dc701a18f3
1: 0x7ff732adf33a - core::fmt::write::h6745c780bcc2c0d4
2: 0x7ff732c36962 - std::io::Write::write_fmt::h62f3b0e8bd2779ea
3: 0x7ff732c3b175 - std::sys::backtrace::BacktraceLock::print::h9fa5706b6e8e39cc
4: 0x7ff732c3cf43 - std::panicking::default_hook::{{closure}}::hfe0ee4d108074dd6
5: 0x7ff732c3cdbc - std::panicking::default_hook::hf6cbe6d722f1fc76
6: 0x7ff732c3dbc7 - std::panicking::rust_panic_with_hook::h616e44b5edd444ca
7: 0x7ff732c3d953 - std::panicking::begin_panic_handler::{{closure}}::h7437a29cd6f5251a
8: 0x7ff732c3bd5f - std::sys::backtrace::__rust_end_short_backtrace::h4da95e3fab5131cb
9: 0x7ff732c3d5be - rust_begin_unwind
10: 0x7ff732add381 - core::panicking::panic_fmt::hbb6255cf869c53d5
11: 0x7ff732ae50ee - core::slice::index::slice_start_index_len_fail::do_panic::runtime::hdb90a6866ceaeb50
12: 0x7ff732ae1b9f - core::slice::index::slice_start_index_len_fail::h91c66d101cc07dd3
13: 0x7ff732b30bba - grav1synth::parser::BitstreamParser<_>::get_grain_headers::h3d32744fc893214d
14: 0x7ff732b3caa2 - grav1synth::main::hc7aa59e60464af47
15: 0x7ff732b06e86 - std::sys::backtrace::__rust_begin_short_backtrace::h52e079443b636f20
16: 0x7ff732b06ded - std::rt::lang_start::{{closure}}::h500b239aea93eb8e
17: 0x7ff732c2f8a2 - std::rt::lang_start_internal::h40d955484821e168
18: 0x7ff732b4fead - main
19: 0x7ff732a41318 - __tmainCRTStartup
20: 0x7ff732a41426 - mainCRTStartup
21: 0x7ffd28a654e0 -
22: 0x7ffd2938485b -