Overflow ParseIntError in scan_listitem

[killercup]

Running this fuzzer script for a few seconds returns

thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: ParseIntError { kind: Overflow }', /checkout/src/libcore/result.rs:860

which according to the backtrace is from this code here.

This input it crashed on was this:

4444444444444444444444444444444444444444444444444444444444!

or, as base64:

NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NCEK