index out of bounds while parsing some ts file

[lu-zero]

I started to look at your implementation and sadly it seems to hate the ts samples I'm trying it with:

❯ RUST_BACKTRACE=1 cargo run --example pcr_measure ~/Samples/mpegts/solidaria-spts.ts
    Finished dev [unoptimized + debuginfo] target(s) in 0.02s
     Running `target/debug/examples/pcr_measure /Users/lu_zero/Samples/mpegts/solidaria-spts.ts`
thread 'main' panicked at 'index out of bounds: the len is 0 but the index is 0', src/parser/payload.rs:86:40
stack backtrace:
   0: rust_begin_unwind
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/panicking.rs:584:5
   1: core::panicking::panic_fmt
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/panicking.rs:142:14
   2: core::panicking::panic_bounds_check
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/panicking.rs:84:5
   3: mpegts::parser::payload::parse_program_map
             at ./src/parser/payload.rs:86:40
   4: mpegts::parser::payload::parse_payload
             at ./src/parser/payload.rs:342:22
   5: mpegts::parser::packet::parse_some_packets
             at ./src/parser/packet.rs:63:24
   6: mpegts::parser::packet::parse_next_packets
             at ./src/parser/packet.rs:18:10
   7: pcr_measure::main
             at ./examples/pcr_measure.rs:34:19
   8: core::ops::function::FnOnce::call_once
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/ops/function.rs:248:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.