Dont yield fatal parse-error on invalid directies

Currently the parser stops on an invalid directive, it would be better if the error was not fatal and parsing continued.

Reduced test-case

<!-- [html-validate-foo] -->
<!-- [html-validate-bar] -->

## Configuration

N/A

## Expected result

Two errors: one for each directive (and other later errors)

## Actual result

Single error for the first directive.

## Version

N/A