Handle parse errors gracefully

[avhetman]

Sometimes, a malformed base64 or hexadecimal string is provided as input. When this happens, an error like this can happen: UnhandledPromiseRejectionWarning: Error: Binary read error sectionLength: 2730 + 3 !== data.length: 15 at parseSCTE35Data

We need to either have some sort of validation here or maybe even a try catch block and output an error elucidating the reason we were not able to parse the string.