Don't throw errors if they are ParsingErrors.
Don't throw errors if they are ParsingErrors.

Instead report them to the consumer of vtt.js.
This was a regression caused by commit:
e55e9c2e8b5e972b324ae72b867c711fa59a5ae5

gkatsev/vtt.js,gkatsev/vtt.js,mozilla/vtt.js,mozilla/vtt.js