[CustomParseFormat] Invalid date when passing just time values

[lbittner-pdftron]

When trying to create a dayjs object using the format HH:ss, the result is "Invalid Date". Here is a minimal example to reproduce:

import dayjs from "dayjs-ext";
import customParseFormat from "dayjs-ext/plugin/customParseFormat";

dayjs.extend(customParseFormat);

const r = dayjs("12:12", { format: "HH:ss" });
console.log(r); // invalid date

Here's the runnable code as well:
https://codesandbox.io/s/pkl826wrj?module=%2Fsrc%2Findex.js

Thanks for your time!