panics on non-utf8 data

[symphorien]

when running ttags on a local clone of nixpkgs, I got:

$  ttags .                                                                 
thread 'main' panicked at src/tagger.rs:83:63:
called `Result::unwrap()` on an `Err` value: Utf8Error { valid_up_to: 12, error_len: Some(1) }
stack backtrace:
   0: rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::result::unwrap_failed
   3: ttags::tagger::Tagger::read_and_parse
   4: <core::iter::adapters::flatten::FlatMap<I,U,F> as core::iter::traits::iterator::Iterator>::next
   5: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter
   6: ttags::App::run
   7: ttags::main
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

[npezza93]

whats the text it's erroring on?

[symphorien]

repro.tar.gz

here it is. It's a git pack file.