bug: if timezone only has hour_offset but the string end with a : will cause panic

[TCeason]

How to reproduce

dtparse is a good project that can resolve more parse questions. But I find a bug will cause panic:

use chrono::NaiveDateTime;
use dtparse::parse;

pub fn parse_dates(test_dates: &[&str]) {
    for date_str in test_dates {

        match parse(date_str) {
            Ok((naive_dt, _tz)) => {
                println!("Parsing: {}, success: {:?}", date_str, naive_dt);
            }
            Err(err) => {
                println!("Parsing: {},  - dtparse Failed: {}", date_str,  err);
            }
        }

        println!("");
    }
}

fn main() {
    let test_cases = vec![
        "2000-01-01 12:00:00+00:"
    ];
    parse_dates(&test_cases);
}