Panic on parsing archive

Parsing this archive file seems to cause a panic:

thread 'main' panicked at 'no entry found for key', src/libcore/option.rs:1166:5
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.34/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.34/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:47
   3: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:36
   4: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:200
   5: std::panicking::default_hook
             at src/libstd/panicking.rs:214
   6: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:477
   7: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:384
   8: rust_begin_unwind
             at src/libstd/panicking.rs:311
   9: core::panicking::panic_fmt
             at src/libcore/panicking.rs:85
  10: core::option::expect_failed
             at src/libcore/option.rs:1166
  11: core::option::Option<T>::expect
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libcore/option.rs:345
  12: <alloc::collections::btree::map::BTreeMap<K,V> as core::ops::index::Index<&Q>>::index
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/liballoc/collections/btree/map.rs:1835
  13: goblin::archive::Archive::parse
             at goblin/src/archive/mod.rs:467
  14: goblin::Object::parse
             at goblin/src/lib.rs:312
  15: strand_match::main
             at src/main.rs:25
  16: std::rt::lang_start::{{closure}}
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libstd/rt.rs:64
  17: std::rt::lang_start_internal::{{closure}}
             at src/libstd/rt.rs:49
  18: std::panicking::try::do_call
             at src/libstd/panicking.rs:296
  19: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:80
  20: std::panicking::try
             at src/libstd/panicking.rs:275
  21: std::panic::catch_unwind
             at src/libstd/panic.rs:394
  22: std::rt::lang_start_internal
             at src/libstd/rt.rs:48
  23: std::rt::lang_start
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libstd/rt.rs:64
  24: main
  25: __libc_start_main
  26: _start
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Source:

use std::fs::File;
use std::path::Path;
use std::io::Read;

use goblin::Object;

fn main() {
    let mut f = File::open(Path::new("os.a")).unwrap();
    let mut buf = Vec::new();
    f.read_to_end(&mut buf);
    Object::parse(&buf);
}

ar seems to extract this archive just fine as well.

Reproduce the panic with the linked os.zip archive and the Rust example, then inspect goblin/src/archive/mod.rs:467 and the call path through goblin/src/lib.rs:312. Confirm how the archive differs from one that ar extracts successfully. Done means parsing this archive no longer panics and regression coverage demonstrates the corrected behavior.