Panic when using read_box

extern crate mp4parse;

use std::io::Cursor;

fn main() {
    let mut c = Cursor::new(b"\x00\x00\x00\x04\xa6\x00\x04\xa6".to_vec());
    let mut context = mp4parse::MediaContext::new();
    let _ = mp4parse::read_box(&mut c, &mut context);
}
coreyf@frewbook-pro /t/mp4 (master) [101]> cargo run
   Compiling mp4 v0.1.0 (file:///private/tmp/mp4)
     Running `target/debug/mp4`
thread '<main>' panicked at 'invalid box size', /private/tmp/mp4parse-rust/src/lib.rs:233
Process didn't exit successfully: `target/debug/mp4` (exit code: 101)

panic discovered using afl.rs