🐛Crash on some PDFs

[mrzv]

When I run diff on some PDFs produced by Adobe Illustrator and pipe the output to delta, I get a crash.

For example, redistribution1.pdf:

export RUST_BACKTRACE=1
diff /dev/null redistribution1.pdf | delta

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Custom { kind: InvalidData, error: "stream did not contain valid UTF-8" }', src/main.rs:65:44
stack backtrace:
0a1,2630
   0: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
   1: core::fmt::write
   2: std::io::Write::write_fmt
   3: std::panicking::default_hook::{{closure}}
   4: std::panicking::default_hook
   5: std::panicking::rust_panic_with_hook
   6: rust_begin_unwind
   7: core::panicking::panic_fmt
   8: core::result::unwrap_failed
   9: delta::delta::delta
  10: delta::main
  11: std::rt::lang_start::{{closure}}
  12: std::panicking::try::do_call
  13: __rust_maybe_catch_panic
  14: std::rt::lang_start_internal
  15: main
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

[dandavison]

Thanks for this report and the example PDF @mrzv. This is fixed in master.