Error when arrow keys typed into terminal while `bats` is running

[daboross]

I didn't exactly expect bats to do anything when I pressed the arrow keys, but I also didn't expect it to error?

Here's a stacktrace / output:

                                        🦇
                                      🦇^[[B
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: ParseIntError(ParseIntError { kind: InvalidDigit })', src/libcore/result.rs:1165:5
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.37/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.37/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:76
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at src/libstd/sys_common/backtrace.rs:60
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1028
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1412
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:64
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:49
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:196
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:210
  10: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:473
  11: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:380
  12: rust_begin_unwind
             at src/libstd/panicking.rs:307
  13: core::panicking::panic_fmt
             at src/libcore/panicking.rs:84
  14: core::result::unwrap_failed
             at src/libcore/result.rs:1165
  15: bats::Bats::draw
  16: bats::Bats::run
  17: bats::main
  18: std::rt::lang_start::{{closure}}
  19: std::rt::lang_start_internal::{{closure}}
             at src/libstd/rt.rs:49
  20: std::panicking::try::do_call
             at src/libstd/panicking.rs:292
  21: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:80
  22: std::panicking::try
             at src/libstd/panicking.rs:271
  23: std::panic::catch_unwind
             at src/libstd/panic.rs:394
  24: std::rt::lang_start_internal
             at src/libstd/rt.rs:48
  25: main
  26: __libc_start_main
             at ../csu/libc-start.c:308
  27: _start
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.